Steak, Mushroom, and Spinach

• 1 yellow onion
• 1 lb top sirloin steak, sliced into strips
• ½ tsp garlic powder
• 4 sprays of cooking spray
• ¼ cup olive oil
• 6 cups spinach
• 4 cups white mushrooms, pre-sliced

1. Thinly slice the onion into rings.
2. Season the sirloin with garlic powder, plus a generous pinch of salt and pepper. 
3. Heat a skillet over medium-high heat, then spray it with cooking spray. 
4. When very hot (test by adding a drop of water to the pan; it should evaporate immediately), add the sirloin and sear for 1 minute, then turn and cook for another 1 minute. 
5. Transfer to a plate.
6. Add olive oil to the skillet and return to the heat. 
7. Add onion and season with a pinch of salt and pepper. 
8. Cook 2 minutes, then lower the heat to medium. 
9. Add spinach and white mushrooms. 
10. Cook 3 minutes, until white mushrooms are just softened. 
11. Return the sirloin to the pan and stir to combine. 
12. Season with salt and pepper to taste.