Cook spelt spaghetti (or your preferred noodles) according to package directions. Salt the pasta water plentifully. When done, drain and set aside.
Meanwhile, slice a small steak into thin strips and marinate with salt and pepper.
Put a pan on high heat and spray generously with cooking spray. Stir fry the beef, turning often, until mostly cooked. Add bagged spinach* or arugula and mix until wilted, and then add the cooked noodles, stirring so that they absorb the juices from the beef. Optional: crumble (or melt in!) soft or grated cheese for more flavour.
*I’ve found I much prefer arugula in this recipe, because wilted spinach sometimes gives me a weird after-texture due to the oxalic acid.