Cut the salmon into small, bite-sized pieces. To get a more uniform ceviche, try to cut the salmon pieces to the same size. This will ensure that they cook evenly in the lemon juice.

Finely chop the red onion, cilantro, and garlic. Finely chopped ingredients will marinate more evenly and have a more pleasant texture.

Add the chopped chili peppers to the salmon and stir well. The chili will add a touch of spiciness to the ceviche. If you don't like spicy food, you can omit the chilies or add only one.

Pour in the lemon juice, olive oil, and salt to taste. The lemon juice will cook the salmon and give it a sour and refreshing flavor. The olive oil will add a touch of richness and the salt will highlight the flavors of the salmon and the other ingredients.

Mix well and let marinate in the refrigerator for at least 30 minutes, or up to 2 hours. The marinating time may vary depending on the thickness of the salmon. Thicker salmon will need to marinate for longer, while thinner salmon can marinate for less time. Serve the ceviche cold.