Trim the edges of the bread and smear butter generously to prevent the sandwiches from turning soggy. You can also toast the bread to keep the sandwich crisp for longer.
Spread the Greek yogurt or mayo or cream cheese generously.
Sprinkle chaat masala (optional), red chili flakes, pepper powder and salt. Gently spread the spice powders and salt evenly.
Place onions, cucumber, tomatoes.
Repeat sprinkling the chaat masala, pepper and salt.
Cover with another slice and cut as desired.
Serve tomato cucumber sandwich for breakfast,