Pat the fillets dry and sprinkle all over with salt and pepper. Sprinkle the thyme on the fillets and pat it lightly with your fingers so that it sticks.
Heat a 12-inch cast iron skillet (if you don't have one - get one!) with lid over medium high heat and add 1 tablespoon of the olive oil. Add the salmon and cook until browned on the first side and then flip. About two minutes per side. Transfer to a plate.
Add the shallots to the pan and saute for about 30 seconds. Add the cauliflower, ¼ teaspoon, a few grinds of pepper and the remaining 2 tablespoons of olive oil and toss the cauliflower to coat with the oil. Brown the cauliflower for about 3 minutes without disturbing it. Flip and cook the other side also undisturbed for about 3 minutes. Taste and adjust the seasoning. Pour in the cream and give it a stir (scraping up the browned bits). Top with the fish. Cover and cook over low heat about 2 more minutes.
Mound the cauliflower "risotto" into two warmed shallow bowls and top it with the fish. Garnish with the thyme.