Using a very sharp knife, cut tuna (or fish of choice) into neat 1/2-inch cubes. Transfer the cubed fish to a medium bowl and stir in the red onion and lime juice.

Let the fish marinate for 10-25 minutes depending on how “cooked” you prefer your fish.

While the fish is marinating, heat a small saucepan over medium-high heat. Once the pan is hot (very hot, almost smoking, but not quite), toss in the rice. Leave enough room so the rice is in a single layer and has enough room to move around.

Shake the pan from time to time so the rice doesn’t burn. Once you hear the rice pop, it’s done. It usually takes about 2 minutes. Be careful not to burn. Set aside to cool.

Once fish is marinated to your liking, lightly toss in cilantro, mango and avocado to coat. Season to taste with salt and pepper. Top with thinly sliced serrano pepper and sprinkle with the puffed rice. Serve immediately.