Bring a large pot of water to a boil then season generously with salt and add penne. Cook until al dente then drain pasta and set aside. Keep the cooking pot out as you’ll use it again at the end.

When the pasta is halfway done cooking, heat extra virgin olive oil in a large, 12"+ skillet over heat that’s a touch above medium. Add red onion, season with salt and pepper, then saute until crisp-tender, 3-4 minutes. Add garlic then saute until very fragrant and light golden brown, 1-2 minutes, being very careful to not let it burn. Add tomatoes then saute until they begin to soften, 1 minute, using the juices to help scrape up any brown bits from the bottom of the skillet. Add baby spinach then saute until it begins to wilt, 1 minute — I like to switch over to tongs to help mix all the vegetables up. If pasta is still cooking at this time, remove skillet from heat so spinach doesn’t overcook.

Place the pasta cooking pot back over low heat then add Balsamic Vinaigrette, drained pasta, and spinach mixture then stir until the dish is heated through and spinach is tender. Scoop into bowls then top with parmesan or feta cheese.