Pour ¼ cup balsamic vinegar into a small saucepan and heat it to a gentle boil.
Reduce the heat to low and let it simmer for 10–15 minutes while stirring occasionally, until reduced and thickened. Remove from the heat and set aside.
Preheat the oven to 400 F.
Prepare the salmon marinade: Place the olive oil, honey, garlic, salt, and pepper in a small bowl and whisk well. Set aside.
Pat the salmon filets dry and place them skin-side down on a greased baking pan.
Spoon the honey marinade onto the top of the salmon filets.
Bake the salmon for 12–15 minutes, spooning any pooled liquid back onto the filets halfway through baking.
Meanwhile, make the bruschetta topping by combining the tomatoes, basil, olive oil, vinegar, salt, and pepper in a mixing bowl and tossing to combine. Let it rest for at least 10 minutes.
Spoon the bruschetta topping evenly over the salmon, drizzle the balsamic vinegar reduction on top, and garnish with basil.
Serve the bruschetta-style salmon immediately, on a bed of arugula, if desired.