Preheat your oven to 350°F (176°C).

Grease a 9-inch square or 8-inch round cake pan.

Thaw frozen strawberries and rhubarb in a colander.

Combine the thawed strawberries and rhubarb with ¼ cup of granulated sugar.

In a separate bowl, whisk together the all-purpose flour, baking powder, and the remaining sugar.

Cream together ½ cup of softened butter and 2 eggs until pale and fluffy, then mix in ¾ cup of buttermilk.

Gradually incorporate the dry ingredients into the wet mixture until just combined.

Fold the strawberry-rhubarb mixture into the batter.

Pour the batter into the prepared cake pan and smooth the top.

Bake for 27-30 minutes until golden brown and a toothpick comes out clean.

Allow the cake to cool in the pan for about 10 minutes before transferring to a wire rack.