Bring a wide pot of water to a boil to cook the asparagus. Season scallops with a little salt and pepper. When the water is boiling, set a 10" skillet over medium-high heat and place the olive oil in it. Add the scallops and garlic. Cook scallops 1 minute on each side, or until just cooked through. Remove the scallops from the skillet and set on a plate.
Place the asparagus in the boiling water and cook until just tender, about 2 minutes. Meanwhile, place the skillet back on the heat and add the butter, citrus juice and tarragon. Cook until the butter is melted and the juice is bubbling. Return the scallops to the skillet and heat through 1 minute.
To serve, divide and arrange the asparagus on 2 heated plates. Divide and top the asparagus with the scallops and the butter/juice mixture. If desired, garnish each plate with a 1/2 lemon slice and 1/2 orange slice.