Spread a thin, even layer of softened butter on one side of each bread slice so the outside crisps evenly once it hits the pan.

In a bowl, combine the grated cheese, chopped onion, chopped capsicum, black pepper, red chili flakes, and salt, mashing lightly so the mixture holds together when spread.

Spread the cheese and vegetable mixture generously on the unbuttered side of each bread slice, pressing it in gently so it stays put during toasting.

Heat a tawa or flat pan over medium heat until it is warm enough that a light sprinkle of water sizzles on contact.

Place the slices butter-side down on the hot tawa and toast until the bottom turns golden brown and crisp.

Flip the slices so the cheese-topped side faces down onto the pan and toast until that side also turns golden and crisp at the edges.

Cover the pan with a lid and let the slices sit so the trapped heat fully melts the cheese through the topping.

Take the toasts off the heat and let them sit briefly so the melted cheese firms up just enough to hold together when cut.

Cut each toast diagonally into triangles and serve immediately while the cheese is still warm and stretchy.