Prepare all ingredients.

Slice the onion thinly.

Slice the kimchi to match the size of the onion slices.

Add cooking oil and minced garlic to a cold pan.

Turn on the heat and sauté garlic until it turns golden brown.

Add tuna and stir-fry for about 1 minute.

Add sliced onion and cook until slightly softened.

Add kimchi and stir-fry until well combined.

Add sugar, soy sauce, gochujang, and water. Stir well.

Simmer until the liquid reduces and thickens.

Prepare a fried egg to your liking.

Plate the rice bowl and top with the cooked mixture and fried egg.