Baking spray with flour
1 cup whole milk
3/4 cup all-purpose flour
3 large eggs, lightly beaten
1 teaspoon pure vanilla extract
Kosher salt
3 tablespoons unsalted butter, melted
1/4 teaspoon baking powder
1 1/2 cups grape tomatoes, quartered
1/4 pound fresh mozzarella, cut into 1/2-inch cubes
1/2 English cucumber, peeled and diced (about 1 cup)
1/2 cup loosely packed fresh basil leaves, chopped
1/4 cup extra virgin olive oil
2 tablespoons red wine or balsamic vinegar
Kosher salt and freshly ground black pepper