Heat 1 tablespoon of the olive oil in 2-quart saucepan on medium-high heat. Add 1 tablespoon of the garlic; cook and stir 1 minute until fragrant. Stir in spinach and tomatoes; cook just until spinach is wilted. Add water and bring to a boil. Add couscous, stirring to mix well. Cover saucepan and remove from heat. Set aside.
Meanwhile, pat scallops dry with paper towels. Season with salt and pepper, if desired. Heat remaining 1 tablespoon olive oil in large skillet on medium-high heat until shimmering. Carefully place scallops in pan. Cook without stirring 2 to 3 minutes until browned on bottom. Flip scallops and cook 2 minutes longer or just until cooked through. Remove scallops from pan and keep warm.
Melt 1 tablespoon of the butter in same skillet on medium-high heat. Add onion; cook 2 minutes or until softened. Add remaining 2 teaspoons garlic; cook and stir 1 minute. Stir in wine, heavy cream, lemon juice and dill. Simmer until mixture is reduced to one-fourth of the original amount (to about 1/3 cup), about 5 minutes.
Reduce heat to low; whisk in remaining butter, one piece at a time, until well blended and sauce is creamy. Gently stir in mandarin orange segments and cook just until heated through. Spoon Citrus Dill Butter Sauce over scallops and serve with Spinach and Tomato Couscous.