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Cakes

Blueberry Buttermilk Cake: A Tender Sheet Cake With Lemony Mascarpone Frosting That Stays Soft for Days

A tender blueberry buttermilk cake baked in one pan and finished with a lemony mascarpone frosting.

Prep20 min
Cook30 min
Total50 min
Servings20 pieces

NutritionApproximate, per serving

Calories390 kcal

Instructions

  1. Heat the oven to 350°F (180°C) (conventional, top and bottom heat). Line an 11 1/2×13-inch (29×33 cm) baking pan with parchment paper.

  2. In a large bowl, beat the softened butter (1 cup plus 2 tablespoons / 250 g) with the powdered sugar (2 cups / 250 g) and vanilla until pale and fluffy.

  3. Add the 5 eggs one at a time. Beat each egg for at least a minute, until it is fully combined with the butter.

  4. In a second bowl, whisk the flour with the baking powder.

  5. Add the buttermilk and the flour mixture to the egg mixture in 3 additions, alternating. Mix only gently now, with a spatula or on low speed.

  6. Gently fold in the lemon zest and most of the blueberries (save a few for the top).

  7. Spread the batter evenly in the prepared pan. Scatter the remaining blueberries on top.

  8. Bake at 350°F (180°C) for about 30 minutes. Test with a toothpick to make sure the center is baked through. Let the cake cool completely.

  9. Frosting: In a bowl, beat the softened butter (1/2 cup plus 1 tablespoon / 125 g) with the sifted powdered sugar (1 1/4 cups / 150 g) until fluffy.

  10. Add the cold mascarpone and the lemon juice. Beat only briefly (about 30 seconds), just until the frosting comes together into a firm mass. Be careful not to overbeat.

  11. Spread the frosting over the completely cooled cake and chill until set.

Tips:
  • The buttermilk secret: Buttermilk (or kefir) makes the crumb especially tender. It keeps the cake from turning dense and helps it stay soft for several days.
  • Sugar in the frosting: The original video uses 300 g (2 1/2 cups) of powdered sugar in the frosting. This version uses 150 g (1 1/4 cups) for a more balanced flavor. If you like very sweet frostings, add more.
  • No-frosting version: The cake is delicious without frosting, simply dusted generously with powdered sugar.
  • Other fruit: Use frozen raspberries, red currants or drained apricot pieces instead of blueberries.