In a saucepan heat 1 teaspoon of oil over a high heat. Sauté the shrimp and moisten them with the juice of one-half grapefruit. When the juice is cooked off, set aside the shrimp. Add 1 teaspoon oil, zucchini, salt and pepper and cook until the zucchini is crisp tender. After 1 minute add the steel-cut oats to warm up. Halve the other grapefruit, remove the slices and peel them. Plate the shrimp, tomatoes, zucchini, oats, diced apple, and the peeled grapefruit slices. Whisk the remaining half of grapefruit juice with the extra virgin olive oil, salt and pepper to taste. Season the salad with the sauce, stirring gently.