In bowl add chopped onion, chopped capsicum, black pepper powder, coriander leaves, chopped green chili, salt and mix well.
Take a bread slice and apply (spread) butter on both side. And do the same with one more slice. now place vegetable 1/2 mixture on a bread slice. Spread and cover the vegetable with the other slice. Do the same for the other 2 slices.
Now heat a flat iron skillet. Roast the stuffed bread slices golden brown on both sides and serve.