Add tomatoes and red onion to a bowl. Drizzle with olive oil, balsamic vinegar, salt & pepper. Toss to combine and set aside.
Heat 3 tbsp. of olive oil in a pan over medium heat. Add bread, dried basil and a pinch of salt & pepper to the pan. Cook, tossing regularly, until bread is toasted on all sides. Remove the bread from the pan and set aside.
To assemble combine tomatoes, onions, bread, arugula and basil in a bowl. Add additional olive oil, balsamic vinegar, salt & pepper to taste.