In a bowl, whisk 2 eggs, 1 finely chopped onion, 1 finely chopped tomato, 1 finely chopped green chilli, a handful of chopped coriander leaves, 1/4 teaspoon turmeric powder, 1/4 teaspoon red chilli powder, salt to taste, and 1/4 teaspoon black pepper powder.
Heat 1 tablespoon oil in a non-stick pan over medium heat. Pour the egg mixture into the pan and spread it evenly. Cook the omelette until it is golden brown on both sides, flipping it once.
Meanwhile, toast 4 slices of bread until they are golden brown and crispy.
Place the cooked omelette on one slice of toasted bread, and cover it with another slice. Cut the sandwich diagonally into two halves. Repeat the process for the remaining bread slices and omelette.