Heat oil in a small pan on medium heat, add the chopped onion and cook till they turn translucent. Add the tomato, salt and pepper. Cook till tomato is slightly soft. Turn off the heat and set aside.
In a small bowl, break 2 eggs, add green chilies (if using), salt and pepper. Whisk well to combine. Set aside.
Heat a medium size nonstick pan on medium heat. Add 1 tablespoon butter and once it melts, add the egg mixture. Swirl around to evenly distribute the mixture in the pan. Dip a bread slice in the still wet egg mixture and flip and place it on the egg. Repeat with another bread slice. Cook till the bottom of the egg is cooked through. Carefully flip both the bread slices and cook on the other side.
Once the egg mixture is cooked through, place half of the onion-tomato mixture on one of the bread slices. Press the omelet over the eggs and fold the bread slices over each other. Cook until both sides are nicely golden. Remove from the pan and slice in half and serve right away. Repeat with the remaining ingredients.
Video
Notes
I like whole-wheat or multigrain bread in this recipe, but feel free to your favorite bread. Gluten free bread would work as well.
Some delicious filling ideas:
sautéed mushrooms
cooked spinach
roasted or grilled veggies - zucchini, eggplant, peppers