Preheat your oven to 350°F (180°C) and prepare two 9-inch round cake pans by greasing with butter and lining with parchment paper.

Chop rhubarb stalks into small pieces and sprinkle with 5 tablespoons of sugar; let sit for 30 minutes to macerate.

In a bowl, whisk together the flour, baking powder, baking soda, and salt.

In a separate bowl, beat the butter and 8 oz sugar until creamy. Add eggs one at a time, incorporating well.

Mix in half of the dry ingredients and crème fraîche, then add the rest of the flour mixture until just combined.

Fold in the macerated rhubarb and pour the batter into prepared pans, spreading evenly.

Bake in the preheated oven for about 40 minutes until edges are golden and a skewer comes out clean.

Cool in the pans for about 10 minutes before inverting onto a plate.