Creamy Cajun Stuffed Salmon

Name: Creamy Cajun Stuffed Salmon
Ingredients: 1 c. frozen spinach, defrosted and squeezed dry; 4 oz. cream cheese, softened; 0.5 c. shredded sharp cheddar (about 2 oz.); 0.25 tsp. garlic powder; 1 tbsp. salt-free Cajun seasoning, divided; 2 oz. jumbo lump crab (about 1/2 c.), picked through; 4 (8-oz.) salmon fillets, about 1 1/2 thick; 1 tbsp. extra-virgin olive oil; 2 tbsp. fresh lemon juice; 1 tbsp. unsalted butter