Bring 1 inch of water to a boil in a large saucepan. Put asparagus in a steamer basket, place in the pan, cover and steam until tender-crisp, about 4 minutes. Transfer to a large plate, spreading out to cool.

Combine chili powder, garlic powder and 1/4 teaspoon salt on a plate. Dredge fillets in the spice mixture to coat. Heat oil in a large nonstick skillet over medium-high heat. Add the fish and cook until just opaque in the center, gently turning halfway, 5 to 7 minutes total. Divide among 4 plates. Immediately add lemon juice, the remaining 1/4 teaspoon salt and asparagus to the pan and cook, stirring constantly, until the asparagus is coated and heated through, about 2 minutes. Serve the asparagus with the fish.