Line a rimmed baking sheet with foil and then rub with a bit of avocado oil to prevent sticking. Lay the steak on the prepared sheet and sprinkle with salt and pepper to taste. Broil on high for 4-5 minutes per side. Remove from oven and allow the steaks to rest for 10 minutes before slicing against the grain.

While steaks cook, prepare the salad. Heat the oil in a large nonstick pan over medium-high heat. Add the onion and salt and cook, stirring occasionally until the onions are soft and translucent, about 5 minutes. Add the garlic and cook until fragrant, about 1 minute more. Add the balsamic and cook until little to no liquid remains. Then add the artichoke hearts and spinach, stirring and turning to wilt the spinach lightly. Serve along with the steak, sprinkled with red pepper flakes, if desired.