Sprinkle the shrimp lightly with salt and pepper. Zest strips from the lemon, being careful not to get any white pith. Squeeze the lemon to get 1 tablespoon juice.

Put a 12-inch skillet (not nonstick) over medium-high heat for 1-½ minutes.  Add 2 tablespoons of the oil and once it’s simmering add the shrimp in a single layer.  Cook until the shrimp browns nicely, for about 1 minute.  Flip the shrimp and brown the second side, about 1 minute.  Transfer to a large plate.  The shrimp should be a little underdone.

Reduce the heat to medium, and add the remaining 4 tablespoons of oil, and the garlic and cook, tossing, until the garlic starts to sizzle steadily, about 30 seconds.  Add the asparagus, lemon zest, and red pepper flakes, sprinkle with ½ teaspoon salt and cook, tossing often, until the garlic is golden brown and the asparagus looks blistery in places, 2 to 3 minutes.  Add the broth, cover, with the lid ajar, and cook until the asparagus is just tender, 1 to 2 minutes.

In a small dish, whisk together the cornstarch with 1-tablespoon water, stir into the asparagus mixture, and bring to a boil.  Stir in the shrimp, reduce the heat to low, and cook, tossing, until the shrimp is opaque throughout (cut one in half to check), for about 1 to 2 minutes.  Stir in the 1 tablespoon lemon juice and then add salt, pepper, and additional lemon juice to taste.  Serve immediately with rice or noodles.