Baked in a 26 cm round cake form, here is the recipe:
2 tsp vanilla sugar
3 egg yolks
1 tsp baking powder
1 or 2 tbsp orange juice
70 g corn starch
175 g flour
~ 750g rhubarb
3 egg whites
pinch of salt
150 g sugar
75 g ground almonds
1 tsp lemon juice
I peeled the rhubarb (which was unnecessary because it turned out super soft and would have looked even better with the red coloring) and cut it in ~2cm pieces. The orange juice is optional and approximate. I had an orange lying around and the only thing I could think of was squeezing it, drinking some, and adding some to the cake. The dough was spread int he pan, and the rhubarb is simply put on top. It looks like too much rhubarb, but it will turn out great.
I baked the cake in the preheated oven at 375F (190C) for 28 minutes.
During the last few minutes I made the meringue by beating the egg whites with the salt until fluffy, then slowly adding the sugar while continuing to beat. I read somewhere that the acid in the lemon juice is supposed to make the meringue stiffer, so in it went. The almond meal was folded in last with a spoon.
The meringue is spread on top of the cake and then returned to the oven. For baking the meringue I reduced the temperature to 350F (175C) and baked the cake for an additional 23 minutes.
Lucky me it looks like it will be windy on Monday and Tuesday, so I have an excuse for eating lots of cake now since I can work it off again on the water soon...