In a small mixing bowl, crack the eggs and whisk them vigorously until light and frothy. Add the chopped red onion, cilantro, green chili, turmeric powder, garam masala, and salt, then whisk again until the ingredients are evenly distributed.

Heat a wide non-stick skillet or tawa over medium heat. Add the butter and allow it to melt, tilting the pan to ensure it coats the cooking surface evenly.

Pour the spiced egg mixture into the center of the hot skillet, swirling the pan slightly so the eggs spread into a wide, thin circle. Cook for about 30 seconds until the bottom begins to set but the top is still runny.

Quickly place the two slices of bread side-by-side in the center of the wet omelette. Press them down lightly to absorb some of the egg, then immediately flip both bread slices over so both sides are coated.

Let the omelette cook for another 1 to 2 minutes until the bottom is golden brown and fully set. Using a large spatula, carefully flip the entire omelette and bread structure over to cook the other side.

Fold the overhanging edges of the omelette inward over the bread slices. Fold one slice of bread onto the other, creating a neat sandwich, and cook for a final 30 seconds until the bread is lightly toasted. Serve immediately while hot and crispy.