Take ½ of a medium-sized onion and place it on a chopping board. Hold the onion firmly in one hand and use a sharp knife to finely chop the onion.

Transfer the chopped onions to a mixing bowl.

Finely chop 1/4 cup of carrots in the same way and add it to the onions.

Place a red bell pepper on the chopping board, and slice off the top and ends of it.

Remove the seeds inside and finely chop ¼ cup of red pepper.

Do the same thing with green bell pepper and chop ¼ cup of small pieces.

Transfer the capsicums to the mixing bowl.

Take ½ of a large-size cucumber and place it on the board. Cut into small pieces and add them to the vegetables in the bowl.

Take 1 medium-sized tomato in half and remove the seedy part.

Finely chop the remaining part of the tomato and add the small pieces to the mixing bowl.

Sprinkle ½ tsp of salt and pepper over the vegetables.

Add ½ tsp of chili flakes for spiciness.

Measure out 6 tbsp of mayonnaise and add it to the mixing bowl with vegetables and seasonings.

Mix with a spatula, combine all the ingredients, and set the vegetable mixture aside for later use.

Take 6-8 slices of white bread and put one slice on a flat surface. Use a knife to cut off the crusts of the bread slice.

Spread 1 tsp of butter on one side of each bread slice.

Repeat the steps for all bread slices.

Take a generous amount of vegetable mixture that you prepared earlier and put it onto a slice of buttered bread.

Spread the filling evenly using a spoon or spatula.

Place another slice of buttered bread on top of the bread to secure the filling. Gently press down the bread to ensure it's positioned properly.

Cut the vegetable sandwich in half, serve it on a plate, and enjoy the deliciousness!