Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes. (Firm or slightly undercooked orzo works best for this dish.) Drain, transfer to a mixing bowl, and set aside.
Heat olive oil and butter in a large skillet over medium high heat, stirring to blend. Stir in garlic, basil, and red pepper flakes, and reduce heat to medium. Stir in pine nuts and cook until lightly browned. Add spinach, cover, and cook on low heat for 5 minutes, or until spinach is wilted.
Toss spinach mixture with orzo pasta. Portion onto serving plates with a drizzle of balsamic vinegar and a sprinkling of crumbled feta cheese and chopped tomatoes. Allow guests to adjust seasoning with salt, as needed. Enjoy!