Preheat your oven to 350°F (180°C) and grease two round baking pans with unsalted butter.

Slice the rhubarb stalks and toss with sugar to macerate. Let sit or briefly braise until tender.

Sift together flour, baking powder, baking soda, and salt. Set aside.

Cream butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each addition.

Fold in half of the sifted flour mixture, then add crème fraîche and mix lightly. Add remaining flour and vanilla, stirring gently.

Pour batter into prepared pans and layer with rhubarb.

Bake for approximately 40 minutes until golden brown and a skewer comes out clean.

Cool in pans for about 10 minutes, then flip onto a serving plate and cool completely before slicing.