Season salmon: Pat salmon fillets completely dry on all sides using paper towels (dry skin guarantees maximum crispiness). In a small ramekin, mix garlic powder, smoked paprika, 1/2 teaspoon salt, and black pepper. Rub the seasoning blend evenly over the salmon flesh and skin.
Sear to crispy perfection: Heat olive oil and 1 tablespoon of butter in a large heavy skillet (cast-iron or stainless steel) over medium-high heat until hot and shimmering. Place salmon skin-side down (if skin-on) and sear undisturbed for 4 to 5 minutes until skin is deeply golden and crispy. Gently flip and sear flesh-side down for another 2 to 3 minutes until cooked to medium (about 130°F / 55°C internally). Transfer salmon to a plate and tent loosely with foil.
Sauté aromatics: In the same hot skillet over medium heat, melt 2 tablespoons of butter. Add minced garlic, sliced sun-dried tomatoes, and crushed red pepper flakes. Sauté for 1 minute until fragrant and garlic turns pale golden.
Simmer cream sauce: Pour in chicken broth (or white wine), scraping up all flavorful browned bits stuck to the skillet bottom. Whisk in heavy whipping cream and remaining 1/4 teaspoon salt. Bring to a gentle simmer and cook for 3 minutes until sauce lightly thickens and coats the back of a spoon.
Wilt spinach & melt cheese: Lower heat to low. Add fresh baby spinach and stir continuously for 1 to 2 minutes until just wilted. Whisk in freshly grated Parmigiano-Reggiano until melted and completely smooth. Remove from heat and stir in lemon juice and chopped fresh basil.
Assemble & spoon sauce: Nest the seared salmon fillets back into the bubbling skillet, spooning luscious Tuscan cream sauce over the fillets while leaving the crispy top crust exposed. Garnish with extra basil, lemon rounds, and cracked pepper. Serve hot!