Simple and casual are the keys to summer entertaining, and a potluck brunch fits the bill perfectly. You prepare the main dish—two tarts that rely on store-bought puff pastry, so they come together quickly yet look impressive. Then ask your guests to bring the rest of the food, including raspberry-lemon muffins and a refreshing watermelon salad with basil and feta. Now you can relax and enjoy the party. After all, it’s summer and the entertaining is easy!