Chop red onion and chili pepper. Mix red onion, chili, lemon juice, olive oil, a pinch of salt, and pepper in a bowl.
Cut salmon filet into 1cm cubes. Put them in the bowl with marinade, and mix them all together. Let it marinate for about 15mins.
Cut avocado into 0,7-1cm pieces. Mix it with a pinch of salt and lemon juice.
Place an 8cm baking ring in the middle of the serving plate. Spread the avocado into the bottom of the ring. Place salmon as the next layer. Pat down gently to compress, then carefully remove the ring.
Garnish with chopped scallions, a drizzle of olive oil and enjoy!