Pat salmon fillets thoroughly dry on both sides with paper towels. Season both flesh and skin sides evenly with 1/2 tsp salt and 1/4 tsp black pepper.

Heat 1 tablespoon olive oil and 1 tablespoon butter in a large 12-inch cast iron skillet or stainless skillet over medium-high heat until shimmering hot.

Place salmon fillets flesh-side down in the hot skillet. Sear undisturbed for 4-5 minutes until a deep golden, caramelized crust forms.

Carefully flip fillets skin-side down. Cook for another 3-4 minutes until salmon is just cooked through to 125-130°F (52-54°C) for medium. Transfer salmon to a warm plate and tent loosely with foil.

Reduce skillet heat to medium. Add remaining 2 tablespoons butter and minced garlic to the pan drippings, sautéing for 1 minute until fragrant but not browned.

Pour in the halal broth and fresh lemon juice, scraping up all flavorful browned bits from the pan bottom. Simmer for 2 minutes until reduced by half.

Stir in heavy cream, lemon zest, remaining 1/2 tsp salt, and pepper. Bring to a gentle simmer for 3 minutes until the sauce turns velvety and slightly coats the back of a spoon.

Add baby spinach and chopped fresh dill, stirring for 1-2 minutes until spinach is just wilted. Nest the seared salmon fillets back into the skillet. Spoon warm lemon cream sauce over the top, garnish with lemon slices, and serve immediately.