Heat a skillet over medium-high heat. Meanwhile, pat fillet dry with a tea towel or paper towel, then season with salt and pepper.

Add just enough oil to cover bottom of skillet, then allow to heat up. Once oil begins to shimmer, carefully place fillet skin side down into skillet. Using a fish spatula, press down firmly to ensure good skin to pan contact, holding for 30 seconds. Reduce heat to medium. Sear undisturbed until fillet releases easily, about 3 to 4 minutes. Flip carefully, cook for a minute, then transfer to a plate.

In the same skillet, add butter, garlic, shallot, and cherry tomatoes. Season with salt and pepper and cook until allium becomes soft and translucent, about 4 minutes. Burst the cherry tomatoes with a fork.

Carefully pour wine into pan and cook for 1 minute. Stir in spinach and cream, seasoning to taste with salt and pepper. Cook until spinach is wilted, then stir in sugar and parsley. Adjust seasoning as needed.

Return fish to the pan and simmer on low until fish is flaky and cooked to your liking, between 1 to 3 minutes depending on thickness of fillets. Serve immediately.