In a large pot, cook the pasta according to package directions.
In a large bowl, toss together the tomatoes, red onions, half of the minced garlic, salt and pepper, 2 tablespoons of olive oil, 1 tablespoon of balsamic vinegar, 2 tablespoons of the basil. Toss together until well combined, then set aside. This is the bruschetta mixture.
In a large skillet, add the remaining olive oil over medium-high heat. Add the remaining garlic and oregano, then stir to cook for one minute, just until the garlic becomes soft and fragrant. At this time, slowly and carefully add a little bit of the hot starchy pasta water to the skillet (about ¼ cup). Then add the butter and continue stirring until the butter melts.
Drain the cooked pasta and add it to the skillet, tossing gently to coat the pasta with the garlic sauce. Add the lemon juice and mozzarella cheese, then add the tomato bruschetta mixture. Toss together until the pasta is well coated. Season with additional salt and pepper to taste, if desired. Drizzle with remaining balsamic vinegar and sprinkle with remaining basil just before serving.
Notes
Pasta: you can use anywhere from 8 ounces to 12 ounces of pasta for this recipe. I've made it mostly with about 10 ounces of pasta, and find the ratio of pasta to bruschetta topping to be great at that amount.Storage: Allow the pasta to cool completely, then store leftovers in an airtight food-safe container in the refrigerator for up to four days.