Preheat your oven to 400 degrees F. Grease your baking pan (a rimmed baking sheet or anything your fish will fit into) with cooking spray.
Rinse your salmon under cold water and feel for any bones to remove. Pat the fish dry with paper towels.
Place your salmon in your pan (skin side down) and top each piece of fish with one teaspoon of olive oil. Brush the oil or use your fingers to spread it evenly. (Wash your hands if you touched the raw fish.) Sprinkle salt and pepper on the salmon.
Slice your fresh mozzarella into rounds about ½ inch thick (or a little thinner, if you prefer). Place two slices of mozzarella on each piece of salmon, in a single layer. (If your fish is longer, you might be able to fit three slices of cheese.)
Rinse your tomatoes and pat them dry. Slice them in half, then in half again. Place your tomatoes on top of the mozzarella, distributing them across each piece of fish. Sprinkle the tomatoes with garlic powder and black pepper. (You shouldn't need any more salt, since the cheese is salty.)
Bake your salmon for 20 minutes, or until the fish can be flaked with a fork. If your salmon is thin, you might only need 15 minutes.
While the salmon is in the oven, rinse and pat dry your basil leaves. Trim off the stems. Make ribbons of basil (chiffonade) by rolling up each leaf and then slicing it into sections about ¼-inch thick.
To serve, remove the skin (if any) from the bottom of the fish. Top each piece of salmon with basil ribbons and drizzle on balsamic glaze.