1. Preheat oven to 400 degrees Fahrenheit.
2. Coat a sauté or frying pan with nonstick cooking spray; heat over high heat. Add garlic and onion; season with half a teaspoon salt. Lower heat to medium-low; cook for five minutes.
3. Add tomatoes, capers, parsley, and red pepper flakes. Raise heat to medium-high. Cook for five additional minutes, until vegetables release liquid and tomatoes begin to wilt. Stir in half a teaspoon salt, basil, and mustard.
4. Meanwhile, place salmon fillets into a baking pan; coat fish with nonstick cooking spray. Sprinkle with salt and pepper. Top salmon with tomato mixture; bake until fish flakes easily with a fork, about 20 minutes.
5. To serve, place salmon on a plate with bruschetta topping and drizzle with balsamic glaze.