Fill a large pot with water and bring to a boil. Add the cauliflower. Cook until softened, around 8-10 minutes. Drain the cauliflower and add to a blender with the shallot, Parmesan cheese, olive oil, garlic, lemon juice, crushed red pepper, salt and pepper. Blend until smooth, around 30 seconds. Set aside
Coat a medium pan with olive oil. Turn the heat to medium high. Add the salmon and cook for 4-5 minutes on each side. I try to buy thinner fillets when pan searing. If you have a thicker fillet you may need to cook longer. Remove from the pan and set aside. Do not clean out the pan, you will use the juices for the sauce.
To the same pan on medium low heat, add the butter and melt. Add the onions and cook until translucent, around 7-8 minutes. Add the garlic and cook until fragrant, around 1 minute. Add the tomatoes and cook for an additional 4-5 minutes.
Add the cauliflower mixture to the onions and tomatoes. Stir and then slowly add in the chicken broth ½ cup at a time. Mix well. Add in the spinach. Cover the pan for an additional 5 minutes to wilt the spinach and stir.
Add the salmon back to the pan and cover in sauce. Serve and enjoy!