Begin by combining chopped rhubarb and sugar in a large bowl. Allow the mixture to sit for about 15–20 minutes.

While the rhubarb is macerating, prepare your crockpot by spraying the insert with non-stick cooking spray or lining it with parchment paper.

In a separate mixing bowl, combine the dry cake mix with yogurt, stirring gently until just mixed.

Pour the macerated rhubarb mixture into the bottom of the prepared crockpot, ensuring it's spread evenly.

Dollop the cake batter over the rhubarb, carefully spreading it out without mixing the two layers.

Cover the crockpot and set it to cook on low for 3 to 4 hours. Check for doneness around the 3-hour mark.

If you prefer a crispy topping, you can broil the dessert for 2-3 minutes after cooking.

Once cooked, let the cake cool for a few minutes before serving with vanilla ice cream or crème fraîche.