Start by patting the sea scallops dry with paper towels. Season both sides generously with kosher salt and fresh pepper.
Juice half of the lemon and set it aside. Peel and segment the navel orange, removing any seeds. Chop the segments into bite-sized pieces.
In a non-stick skillet, heat the extra virgin olive oil over medium-high heat until it shimmers.
Carefully place the scallops in the hot skillet and sear for about 2-3 minutes on one side without moving them.
Once golden brown, flip the scallops, add the crushed garlic and unsalted butter, and cook for another 2-3 minutes, basting with melted butter.
Remove the scallops from the skillet, squeeze reserved lemon juice over them, and sprinkle the orange segments around.
In a bowl, combine mixed baby greens, baby arugula, and chopped red onion. Drizzle a little olive oil and a pinch of salt and pepper over the greens, tossing gently.
Place the dressed greens on a serving platter or plates, top with the scallops, and serve immediately.
