Start water boiling and cook pasta according to package directions. If you are using any frozen veggies like broccoli, green beans or cauliflower, add them with the pasta to cook together.
Heat the olive oil in a large skillet or sauté pan (big enough to hold the pasta after cooking) over medium-low heat. Add the onions, garlic, seasonings, and any optional fresh vegetables (peppers, asparagus, broccoli, etc) and cook for 3-4 minutes, until done to your liking. Stir in the lemon juice to deglaze the pan.
Drain pasta, reserving some water, and add the pasta to the vegetable mixture in the large pan, along with the tuna and olives.
Stir everything, adding optional red pepper flakes and butter, and enough reserved pasta water to make a thin sauce. Salt to taste.
Serve with grated cheese, if desired.
Notes
Keep any leftover pasta in airtight containers for up to 5 days (less if using a chickpea pasta which can get a bit rubbery).Nutrition has been calculated with no optional vegetables or cheese. Using protein pasta would add 7-9 grams of protein per serving and a few grams more fiber (regular pasta has about 3 grams protein).