sentence: melt butter with oil in a skillet add sliced small red onion and fry sentence: add sugar and balsamic vinegar to it and stir sentence: spread butter on 2 slices of wheat bread and place them on the skillet butter side down sentence: add some grated cheese on top of both the slices sentence: place some caramelized onions over one slice and 2 slices of tomatoes on the other sentence: sprinkle salt on the tomato slices and lay some spinach leaves on top that sentence: put the bread together and press down