Heat butter in a pan
Sauté onion, garlic well until transparent
Add tomato and sauté until mushy
Add all other vegetables, salt and cook well, add water if required
Squeeze lemon juice over and mix well
Spread cheese over a tortilla
Spread cooked vegetables over and again spread cheese
Place another tortilla over and press well so that it sticks well
Heat a pan and cook on both sides for about a minute
Cut the quesadillas into 2 or 4 pieces
Serve hot with salsa sauce