In a skillet filled with boiling water, add the salmon fillet, skin side down, and let it cook for 1 minute.
After this time has passed, remove the salmon from the water and transfer it to a cutting board.
Remove all the skin from the salmon - by doing this step, the skin will come off easily – and cut it into 3 equal pieces.
Season with a pinch of salt, a pinch of black pepper and set aside.
In a large skillet over medium to low heat, add the butter, a drizzle of olive oil and stir until the butter melts completely.
Add the salmon we prepared, and fry until both sides are golden brown.
Remove from the skillet and set aside.
In the same skillet, add the onion cut into thin strips, the crushed garlic cloves, and sauté until lightly golden brown.
Add the mushrooms cut into smaller pieces, the red pepper cut into strips and sauté for another 2 minutes.
Season with the salt and a pinch of black pepper.
Add the spinach leaves, the cooking cream, the water and mix everything to combine.
Then, add the salmon we prepared, and the lemon cut into round slices.
Cover the skillet and let everything cook for 5 minutes.
Serve.