Combine yogurt, horseradish, tabasco sauce, red wine vinegar, and lemon juice in a bowl. Finely dice garlic and add. Combine well. Season with salt and pepper to taste.
Season ribeye steaks heavily with salt and pepper. Bring to room temperature.
Preheat skillet to medium-high heat. Add olive oil and cook steaks 2-3 minutes per side or until desired doneness. Halfway through cooking, add butter, garlic cloves, and rosemary sprig. Baste steak with butter until done. Remove steaks from skillet and rest on a cutting board for 20 minutes before slicing.
Using the same skillet, add chicken broth to deglaze the pan. Bring chicken broth to a boil. Add couscous. Remove from heat and cover skillet for 5-6 minutes until couscous is cooked and all the broth is absorbed.
Slice tomatoes in half. Peel and roughly chop cucumber. Slice green onions. Dice parsley. Add ingredients into the skillet with the couscous and combine. Season with salt and pepper to taste. Add feta cheese at the end.OPTIONAL: Drizzle olive oil over couscous.