Preheat your oven to 350°F and grease a 9-inch square baking pan. Cream together the butter and granulated sugar until it's light and fluffy, which takes about 3-4 minutes with an electric mixer. You'll know it's ready when the mixture looks pale and almost fluffy like a cloud.

Add the eggs one at a time, beating well after each addition so everything incorporates smoothly. Pour in the vanilla extract and mix for another 30 seconds. Don't skip this step because the eggs need to fully emulsify or your cake will have a weird grainy texture that nobody wants.

Combine your flour and baking powder in a separate bowl, then alternate adding the dry mixture and milk to your butter mixture. Start with half the flour, add the milk, then finish with the remaining flour and mix just until you don't see streaks anymore. This is where I always add a pinch more vanilla because honestly you can never have too much vanilla in a cozy layered dessert.

Pour the batter into your prepared pan and bake for 25-30 minutes until a toothpick inserted in the center comes out clean or with just a few crumbs. The kitchen's gonna smell absolutely amazing at this point, I'm not kidding. Let it cool for about 10 minutes in the pan before turning it out onto a wire rack completely.

While your cake cools, whip the cream with powdered sugar until soft peaks form — this means you can lift your whisk and the cream holds a gentle peak for a second before flopping over. Don't overbeat it or you'll end up with butter and nobody wants grainy whipped cream in their summer fruit trifle cozy. I use about 2-3 minutes on medium speed with my mixer.

Cut your cooled cake into cubes about 1 inch wide (they don't need to be perfect). This is the part where you can be messy because you're gonna layer these anyway and imperfect pieces actually work better for absorbing flavor. Plus the rough edges catch more of that vanilla syrup if you brush it on.

Now for the magic part — start layering in a large glass trifle dish or any clear glass bowl. Layer about one-third of your cake cubes on the bottom, then add a third of the mixed summer fruits, then a third of the whipped cream on top. Repeat twice more so you've got three complete layers visible through the glass. The visual is honestly half the appeal of this warm summer dessert.

Top with the chopped pistachios right before serving so they stay crispy and don't get soggy from the moisture. You can make this up to 6 hours ahead if you need to, just add the pistachios at the last second.