Bring 1 inch of water to a boil in a large saucepan. Put asparagus in a steamer basket, place in 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 spice mixture to coat. Heat oil in a large nonstick skillet over medium-high heat. Add fish and cook until just opaque in the center, gently turning halfway through cooking time, 5-7 minutes total. Divide among 4 plates. Immediately add lemon juice, remaining 1/4 teaspoon salt and asparagus to pan and cook, stirring constantly, until asparagus is coated and heated through, about 2 minutes. Serve asparagus with fish.