Preheat oven broiler to low. In a large pot, cook the macaroni pasta in salted water according to package directions. Drain and set aside.
While the pasta is cooking, heat a large skillet over medium heat. Swirl in 1 tablespoon olive oil and add onions. Saute until softened, about 3 minutes. Add garlic and saute for an additional 2 - 3 minutes. Add spinach and salt. Continue to saute until spinach is wilted. Remove spinach mixture from pan and set aside.
Wipe the skillet dry and return to the stove over medium heat. Swirl in the remaining 2 tablespoons of olive oil to skillet. When the oil is hot, whisk in the flour. Continue to whisk while adding a generous pinch of salt, pepper and nutmeg. Whisk over medium heat until flour smells nutty and is a light golden color. Whisk in milk and bring mixture to a boil while stirring frequently. This mixture will thicken. Simmer for about 5 minutes then remove from burner and stir in the Havarti cheese until the cheese is melted. Add feta and whisk, feta will get melty, but will stay in chunks.
Spoon in the sauteed spinach mixture, chopped olives, capers and sun-dried tomatoes. In a casserole dish, combine all of the ingredients with the macaroni. Mix well and top with bread crumbs. Brown under broiler for about 5 minutes before serving.