cut onion into pinky size

heat oil and stir fry onion stripes (or microwave for 2 min)

put tsuyu and water to a pot to boil

add onions and tuna in the boil tsuyu base and cook for 20 min on low

turn off the stove and put beaten eggs on top, put the cover back for 5 min until the eggs are cooked

put on top of rice