Rhubarb Pie (Rabarberu rausis)

Adapted from Latviešu ēdieni

Dough:

• 250 g ap flour
• 125 g milk (about 1/2 cup)
• 40 g + 1 tsp sugar
• 75 g butter
• 1/2 egg
• 3 g salt
• 1 1/2 tsp active dry yeast
• 1/4 c warm water (100 - 110F)

Filling:

• 400 g rhubarb, peeled and coarsely diced
• 50 g sugar
• 75 g sour cream
• 2 egg yolks
• buttermilk or kefir
• 1/2 tsp vanilla extract

To make the dough: Combine yeast with warm water and 1 tsp of sugar, stirring to dissolve, let sit for 10 minutes until doubled in volume. Mix in flour, half an egg, salt, butter and milk. Place in an oiled bowl on a rack over boiling/steaming water, cover loosely with a clean kitchen towel and let rise for 1.5 to 2 hours until doubled.

On a floured surface, roll out dough to about 1/2" thickness. Put the flattened dough into a 9x9 greased baking dish (or slightly larger, if you have it) and let rise for another hour.

Preheat oven to 350F.

To make the filling: Whip sour cream and egg yolks together, adding in vanilla extract, remaining sugar gradually. Thin with buttermilk or kefir if needed to obtain a pourable consistency (like a thick pancake batter). Peel rhubarb and coarsely dice, then mix with about 30 g sugar and set aside.

Preparing the finished cake: Indent the edges of the dough like a pizza so that a small 1/2" to 1" wide raised edge will prevent the filling from soaking the bottom of the dish. Spread rhubarb evenly over the dough then pour the batter over.

Bake at 350F for 40 - 50 minutes until golden brown. If a knife or toothpick inserted in the center comes back clean, it should be ready to come out.