In a large pan, over medium high heat, melt butter and heat oil. Add in onions and peppers, cook for 3-5 minutes, until onions are translucent. Stirring occasionally.Add in mushrooms and tomatoes, cook an additional 1-2 minutes, until tomatoes soften a little. Stirring occasionally.Season with salt and pepper, add in lemon juice (if desired).Add in zucchini noodles, toss it with all the ingredients, lower heat to medium, and cook an additional 3-4 minutes, until zucchini noodles heat up.