Baked Barramundi with Asparagus, Onions, & Shiitake

1 1/2 pounds fresh or frozen Barramundi fillets
olive oil
1 tsp Celtic sea salt
1/2 tsp freshly-ground black pepper
1 large onion, sliced thinly into half-moons
4-6 garlic cloves, diced
1 bunch asparagus, cut into bite-sized pieces
6 oz. shiitake mushrooms, sliced
1 lemon

Preheat oven to 400ºF. Pat fish dry with paper towel and place on parchment-lined baking sheet. Drizzle with olive oil and season with Celtic salt and black pepper. Bake 15-20 minutes without flipping.

While fish is cooking, heat 2 tbsp olive oil over medium-low heat and add onions to sauté for 5-7 minutes. Add garlic and shiitake mushrooms, and stir while cooking 2-3 minutes. Add asparagus and stir 2 more minutes, or until asparagus is a bright green color. Season with Celtic salt and pepper and remove from heat.

Transfer to serving dish and top with cooked fish. Squeeze fresh lemon over dish and enjoy immediately.