I've hit that same dilemma before. A curd and a lemon meringue are different in final texture. And able to slice i believe it needs corn starch... (?, at least in my limited pie skills)
This one is close and what i have tried, but i added cornstarch like the 'grandma' link below.
http://onevanillabean.com/2010/05/10/storybook-macarons-lemon-blueberry-and-rhubarb-strawberry-macarons/

I always add a few strawberries as the color can come out a bit odd. Once i added blueberries. Very strange color, lol. Now i just place whole blueberries on top. I've not made a meringue in years but should. It was a childhood favorite.

Martha's recipe team are often a bit off. Rarely 'tried and true'. I always need to adjust. A recent search for rhubarb on her site had a lengthy list of recipes and most of them used a chunky chutney over and over with hardly a variation in ingredients.

I usually just stick to rustic tarts using tapioca. But very interested in your outcome as i am swimming in rhubarb right now. Just made three sauces this morning...dreaming up a forth.

Here is a link that might be useful: lemon meringue

So, I did make a rhubarb meringue tart, and it turned out really great. Everyone enjoyed it.

I ended up following the recipe I found at the Nothing-in-the-house blog. I would make this again, but with some adjustments.

I would not make it with the pecan crust. IMO, the pecan and rhubarb flavors were too competitive. A plain shortbread crust would be my preference for next time.

The filling was good. Next time, I might reduce the sugar a bit. My preference would be for the filling to be more on the tart side. I would also add a little lemon juice or zest to brighten the flavor.

There was a typo in the crust recipe, as there were no sugar in the ingredients list, but it was mentioned in the instructions, so I just used 1/4 cup sugar. But as I said before, I would substitute a plain crust.

Recipe is here: link to blog is below

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Rhubarb Meringue Tart with a Pecan Shortbread Crust

Ingredients

For crust:
1 c. pecans, roasted
1 3/4 c. all-purpose flour
2 tsp. baking powder
9 Tblsp. butter
1 egg
1 egg yolk
1 tsp. vanilla extract (I used vanilla-bourbon)
zest of one small orange (I used a clementine)

For filling:
3 c. fresh rhubarb, diced
1/4 c. + about 1/2 c. water
1 1/4 c. sugar
1/4 c. cornstarch
1/4 tsp. salt
5 egg yolks (save whites for meringue)
3 Tblsp. butter, cut into chunks

For meringue:
5 egg whites
1 tsp. cream of tartar
1/4 c. sugar

Directions
For crust:
1. Combine roasted pecans, flour, sugar, and baking powder in a food processor and pulse until pecans are finely ground. Add cold butter chunks to the pecan mixture and process until mix is the size of small peas. Add egg, egg yolk, vanilla extract and orange zest and pulse just until dough begins to form. Remove pastry dough from the food processor and wrap tightly in plastic wrap. Chill for at least one hour and up to 1 day.

2. After at least one hour, preheat oven to 350 degrees F and lightly grease and flour the bottom and sides of a 9-inch tart pan. Remove the dough from the fridge. I rolled out the dough first(which was a little difficult, as it was crumbly), but you can also just press it into the bottom and sides of the tart pan. The bottom crust should be slightly thicker than the sides. Place crust in the freezer for about 10 minutes, then line with parchment paper and pie weights. Bake for about 20 minutes or until crust is dark brown. Remove pie weights and bake for 5 more minutes. Take from oven and let cool.

For filling:
1. Combine diced rhubarb and 1/4 c. water in a saucepan and bring to a boil over medium heat. Let cook until rhubarb is soft and begins to break down. With an immersion blender (or a stand blender), purée until smooth and set aside to cool slightly. Once cooled, add enough water to bring purée to 1 1/2 c. (this should be about 1/2 c. of water).

2. Add sugar, salt, and cornstarch to the purée mixture and cook over medium heat until it begins to thicken. Add in egg yolks, whisking after each addition. Continue to cook until mixture coats the back of a spoon, or reads 185 degrees F on a candy thermometer. Remove from heat and stir in the butter. Let cool to room temperature. Once cooled, pour filling into pie crust, cover with plastic wrap and place in the fridge for about 2 hours.

For meringue:
1. Once filling has chilled for 2 hours, preheat oven to 375 degrees F. In a medium mixing bowl, mix egg whites and cream of tartar on high until egg whites begin to form medium peaks. Continue to beat eggs, gradually adding in sugar. Continue to beat eggs until they are glossy and can form stiff peaks. Spread over rhubarb filling, making sure the meringue seals the edge of the pie. Use the back of a spoon to curl meringue decoratively. Bake for 12-15 minutes or until egg whites begin to brown. Serve chilled or at room temperature.

Here is a link that might be useful: Rhubarb Meringue Tart with a Pecan Shortbread Crust