Combine olive oil, lemon juice and parsley in a small bowl. Whisk to combine. Season with sugar (if using), salt and pepper.
Toss tomatoes and avocados in half the dressing. Set aside.
Arrange orange slices on a plate; scatter with onion rings. Drizzle with remaining dressing. Spoon tomatoes, avocados, almonds and olives on top of oranges. Serve right away.
