Prepare the cake: Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, or line them with parchment paper circles.

1. Make the lemon cake batter: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. In a large mixing bowl, beat the softened butter and sugar together until light and fluffy, about 3-4 minutes. Add the eggs one at a time, beating well after each addition. Stir in the lemon zest, lemon juice, and vanilla extract. Add the dry ingredients alternately with the buttermilk, starting and ending with the dry ingredients. Mix until just combined.
2. Bake the cake: Divide the batter evenly between the two prepared cake pans. Smooth the tops with a spatula and bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
3. Make the lemon curd: In a medium saucepan, combine the lemon juice, lemon zest, and sugar. Heat over medium heat until the sugar dissolves. In a separate bowl, whisk the egg yolks until smooth. Slowly pour the hot lemon mixture into the egg yolks while whisking constantly to temper the eggs. Pour the mixture back into the saucepan and cook over low heat, stirring constantly until it thickens and coats the back of a spoon (about 5-7 minutes). Remove from heat and stir in the butter until smooth. Let the lemon curd cool to room temperature.
4. Assemble the cake: Once the cakes have cooled, place one layer on a serving plate or cake stand. Spread a layer of lemon curd over the top. Place the second cake layer on top and gently press down. Spread the remaining lemon curd over the top of the cake, allowing it to drip down the sides slightly.
5. Top with berries: In a bowl, toss the strawberries, blueberries, and raspberries together. If you’d like, drizzle the honey or maple syrup over the berries to sweeten them slightly. Spoon the berries over the top of the cake, letting them cascade down the sides.
6. Garnish and serve: Garnish the cake with fresh mint leaves for a pop of color, if desired. Slice and serve chilled or at room temperature.