Step 1

Stir tomatoes, basil, 3 tablespoons olive oil, red onion, garlic, red wine vinegar, and pepper together in a bowl; let tomato mixture stand at room temperature for 15 minutes, then place in the refrigerator to marinate for 45 minutes.

Step 2

Set oven rack about 6 inches from the heat source and preheat the oven's broiler.

Step 3

Brush one side of each slice of bread with remaining olive oil. Place bread slices, oiled-side-up, onto a baking sheet.

Step 4

Broil until golden brown, about 2 minutes; remove from oven. Spoon tomato mixture evenly over the top of toasted bread slices; drizzle balsamic vinegar evenly over tomato mixture. Serve immediately.