Preheat oven to 230 degrees C. Line a baking tray with foil.
Bring a large pot of lightly salted water to the boil. Cook orzo pasta in the boiling water, stirring occasionally until tender yet firm to the bite, about 10 minutes. Drain.
Mix garlic powder, 4 leaves basil and 1/2 teaspoon salt together in a small bowl.
Place salmon skin side-down on the prepared tray. Brush with 1 tablespoon butter; sprinkle garlic-basil mixture on top.
Bake in the preheated oven until salmon flakes easily with a fork, about 8 minutes. Remove and let rest.
Place chopped bacon in a pan over medium-low heat; cook and stir until crispy, about 4 minutes. Add 1/2 teaspoon salt and the peas. Season with pepper. Cook and stir until peas are heated through, 3 to 4 minutes.
Whisk remaining 3 tablespoons butter, juice from 1 lemon and remaining 1 teaspoon salt together in a bowl. Pour over the cooked orzo and toss to coat. Season with pepper.
Divide orzo among 4 plates; top with salmon and place peas on the side. Garnish with the remaining basil. Drizzle remaining lemon juice on top.