Bring 4 cups water and 3/4 tsp salt to a boil in a saucepan. Whisk in the grits, reduce heat to low, and simmer, stirring often, for 20-25 minutes until thick and creamy. Remove from heat and stir in heavy cream, cheddar, and 1 tbsp butter. Keep warm.

Meanwhile, pat salmon dry and season flesh side with remaining 3/4 tsp salt, pepper, and garlic powder (if using). Heat olive oil in a skillet over medium-high heat. Place salmon skin side down, press gently, and cook 5-6 minutes without moving. Flip and cook 2-3 minutes until just cooked through. Transfer to a plate.

In the same skillet, melt remaining 1 tbsp butter over medium heat. Add garlic and cook 30 seconds. Stir in lemon zest and juice, let bubble for 1 minute until slightly reduced and glossy.

Spoon grits into bowls, top with salmon, and spoon the lemon butter sauce over the top. Serve immediately.