First, cut open the avocado and for each half, make slices or cuts according to how big or small you want your pieces to be. When you cut it inside of the skin/shell, you can simply spoon it out when you're ready.

Heat the olive oil in a large skillet over Medium heat.

Add 1 tortilla to coat the entire pan-side of the tortilla with oil. Then add some of the cheese onto one half of the tortilla. Keep in mind that you will need to split the amount of cheese between each tortilla/quesadilla.

Spread half of the diced tomato and spoon out and spread one half of the avocado over the cheese.

Sprinkle some more cheese over the tomato and avocado, then fold the empty/plain half of the tortilla over the other side of it. Flatten the quesadilla with a spatula.

Cook on that same side until the cheese is gooey and thoroughly melted on the bottom/pan side. Flip the quesadilla and repeat on the other side. It should be about 5 minutes on each side.

Serve with sour cream (optional)