Using your hand, squash together the onions, garlic, ginger, curry leaves, chilies, lemon juice, and salt.
Add the tuna and coconut, and mix until it becomes a sticky mixture.
Shape the mixture into small balls (about 1 inch in diameter).
Add the oil and salt into the flour.
Add warm water and knead until you have a dry, smooth dough. (Add the water gradually to make sure the dough does not turn out too sticky.
Shape the pieces of dough into cups and place filling inside; then close the cups and smooth into balls.
Warm a shallow, non-stick skillet over the stove.
Using a rolling pin, gently flatten out the filled balls into small round circles (about 3 inch in diameter)
When the skillet is warm enough, place the masroshi on them. Keep flipping every few minutes so both sides cook evenly.
If you would like the masroshi to be crispier, then add a cup of grated/shredded coconut to flour when making the dough.
Serving Size 8 - 10 Servings