Yes, just to clarify, I also had to scoop the cakes out too - not just the rhubarb (the cake stuck too the tin). So that was the main part of the problem.

The instructions say to 'cool and turn out'.

When I make an upside down cake, I always loosen the edges of the cake & turn it out of the pan immediately after removing from the oven.

So, I would try doing that rather than letting the cakes cool in the tin before trying to turn them out.

If that doesn't work, you could try cutting parchment paper circles to line the bottom of the tins.

How well buttered were your muffin cups? You could also try dusting them with a little flour after buttering, or you could use muffin cup papers, or try a silicone muffin pan. Or, after baking, run a knife around the outside of the cake part to ensure it is not stuck to the pan.

They were very well buttered - partly because I grew up where you always buttered then floured a pan, so I'm always a bit dubious when they don't say to do that. More and more I'm thinking this would work better as a cake you just do in one loaf pan and then spoon out appropriate servings - easier that way. Hmmm....

Flawed recipe....there is no way in H E doubletoothpicks that rhubarb and sugar will come out of a muffin pan neatly...butter and flour, parchment or whatever.
I might try a modified recipe where I butter the pans well and put in a spoonful of cake batter, then rhubarb and more cake. That may stick as well.
That's when you make a nice yellow cake and some rhubarb sauce with extra brown sugar on top of the stove, and spoon some over the top of each serving of cake.

Or try this

ALMOND RHUBARB CRISP (Serves 6)

1/3 c. whole natural almonds

1 1/4 lb. fresh rhubarb

1/4 c. water

3/4 c. sugar

1/2 tsp. almond extract

1/2 c. butter or margarine, softened

1/2 c. flour

1/4 tsp. salt

Grind almonds in food processor or blender, or chop very finely. Wash and

trim rhubarb; cut into 1" pieces. Place in buttered 1 1/2 qt. shallow

casserole. Combine water, 1/4 c. of the sugar, and almond extract. Pour

over fruit. Cream butter with 1/2 c. sugar, then beat in ground almonds,

flour, salt. Sprinkle dough in large pieces over rhubarb. Bake at 375

degrees for 30 min. or till top is getting golden brown--I find it usually

takes more than the 30 minutes. Serve warm or cooled. (I serve w/ whipped

cream or vanilla ice cream.) Serves 6.

I make rhubarb muffins all the time. Where's the flour in this cake??? That's a huge typo.

It's there, it's the 5th ingredient listed (1 cup all purpose).

Thanks LaLennoxa. I read the recipe twice and went by it both times.

H E double toothpicks........that's so funny...never heard that one before.

Sounds like it's a problem w/ the muffin pan, not the recipe. If you use a non-stick pan, it most likely would come out cleanly. Alternatively, you might bake the cakes in little ramekins or custard cups and serve them unmolded.

Additionally, I find letting cakes & muffins cool in their pans for @ least 10 minutes causes enough steam condensation to make it easier to turn them out. Sliding a thin blade around the edges first definitely helps.

Actually, I did use a non-stick pan. And let it cool while we ate dinner - so at least an hour before we had to carve the cakes out! :-)

Rhubarb is mostly water........when it's on the bottom, with no thickening mixed in, it stays soupy. As written that recipe is not going to turn out of the pan...

Actually, it was quite dry. I actually loved it (taste-wise) as it was, or would have been excellent served with cream, or ice cream.

I'm including pictures to give you an idea how it looked. Again, excuse the messiness, but that's what happened :-)

A picture really is worth a thousand words; those square shapes definitely would make it more difficult to run a sharp blade around to loosen. The fact that they overtopped the molds may also have contributed. Molds look very shallow too - more so than a typical muffin pan.

They make square muffin liners that could work, or I'd just make some muffin liners out of parchment. After cooling a bit they could just be peeled away.

I like your muffin pan liners, Olychick. They're both cute and sophisticated looking.

Slightly OT, but I made Lindac's Rhubarb Almond Crisp today. Subbed ground oatmeal (oat flour) for the wheat flour to make it gluten free and it turned out great.