Add half teaspoon of butter and ¼ teaspoon of oil into a nonstick skillet. While that is warming up, assemble sandwich: take one slice of bread, sprinkle with cheese, top with fresh mozzarella, tomato sliced, spread pesto on the other slice of bread and close to form sandwich.
Place into skillet and cook for ~3 minutes or until brown. Lift with a spatula and add another half teaspoon of butter and ¼ teaspoon oil to skillet and let it swirl around to coat the pan. Flip sandwich and add back to pan. Brown for 2-3 minutes or until cheese has melted.
Notes
If bread is getting too brown and cheese hasn't fully melted, put it in the microwave for about 10 seconds. Note: I like using butter and olive oil, but it's optional really
Recipe by Nutritious Eats at https://www.nutritiouseats.com/grilled-tomato-cheese-pesto/