Preheat your oven to 350°F. Cream together the softened butter and sugar until it looks light and fluffy, which takes about 2 minutes with an electric mixer. Add your eggs one at a time and beat well after each one.
In a separate bowl, whisk together flour, baking powder, and salt. Alternate adding the dry mixture and milk to your butter mixture, starting and ending with the dry ingredients. Mix until just combined — don't overmix or your cake will get dense.
Pour the batter into a greased 9-by-13-inch baking pan and bake for 30-35 minutes until a toothpick comes out clean. The top should be golden and spring back when you lightly touch it. Let it cool completely on a wire rack.
While the cake cools, prepare your fruit layers. Warm the strawberry puree gently in a saucepan over medium-low heat for about 3-4 minutes, then stir in the honey. Do the same with your blueberry compote in a separate pot for consistency.
Once everything's cooled, cut your vanilla cake into 1/2-inch cubes — I usually get about 12 cups total. Don't worry if some pieces are bigger than others because they'll all layer beautifully anyway.
Now for the red white blue trifle sharing magic: start with a thin layer of white cake cubes at the bottom of your trifle dish. Add a layer of whipped cream, then strawberry puree, then more cake. Repeat until you reach the top.
Finish with a final whipped cream layer and garnish the top with fresh strawberry slices and blueberries scattered across. Chill for at least 2 hours before serving so all those layers set up properly and the flavors meld together.