Preheat oven to 350°F (177°C).
Bring water to a boil in a large pot and add kosher salt. While water is coming to a boil, prep bruschetta.
Prep tomatoes, onion, and garlic for bruschetta. Then mix together all bruschetta ingredients (except the bread) in a bowl and season with salt and pepper to taste. Set aside until you are ready to serve.
Once the water is boiling, cook pasta according to the directions on the package. Once tender, drain the pasta, reserving 1/4 cup of the pasta water.
Make Arrabiata sauce: Mince garlic per instruction above. Set a large pan over medium heat. Once hot, add olive oil and garlic; saute for 1 minute. Add the tomato paste and pepper flakes; reduce the heat to low and stir just until fragrant, about 4 minutes. Stir in the tomatoes, and remove from the heat.
Place sliced bread on a baking sheet and bake in the oven until golden brown.
Finish pasta: Add the pasta to the tomato sauce along with a small amount of the reserved pasta water to desired consistency. Stir and toss over medium heat until the pasta is well coated. Season with salt to taste, drizzle with oil, and toss well.
Finish bruschetta: Spoon the bruschetta mixture onto the bread.
Serve: Top the pasta with grated Parmigiano-Reggiano. Enjoy with bruschetta and sparkling water.