1 tablespoon olive oil
1 tablespoon butter
½ sweet yellow onion (such as Vidalia®), thinly sliced
4 patty pan squash, sliced to 1/2-inch-thick pieces
3 cloves garlic, crushed, or more to taste
1 dash lemon pepper
1 ½ cups packed fresh spinach (Optional)
¼ cup chopped fresh parsley
1 tablespoon chopped fresh basil
½ lemon, juiced
1 ½ teaspoons grated Parmesan cheese
salt and ground black pepper to taste
Heat olive oil and butter in a skillet over medium-high heat until foaming, 1 to 2 minutes. Saute onion in the olive oil-butter until tender and translucent, about 3 minutes. Add squash and garlic; season with lemon pepper. Saute mixture until squash is easily pierced with a fork, 5 to 6 minutes.
Mix spinach, parsley, and basil into squash mixture; saute until spinach wilts, about 1 minute. Squeeze lemon juice over mixture and sprinkle in Parmesan cheese; stir well. Season mixture with salt and black pepper.