Heat oil or butter in a large 12″ skillet over medium heat. Once hot, add onion and garlic and sautè for 2-4 minutes, until onions begin to soften and garlic is fragrant.
Add in mushrooms and any other optional diced vegetables you choose (zucchini, bell peppers) and let cook for 5-7 minutes, until veggies begin to soften, and water reduces from mushrooms.
Add in ground beef and seasoning and cook until no pink remains, about 5 minutes.
Add in jar of marinara or spaghetti sauce. Reduce heat to a simmer for 5 minutes. Taste and adjust seasoning as desired.
Serve hot with optional garnishes and over pasta, zucchini noodles, or spaghetti squash.
