Brown and crumble the ground beef in a large pot over medium heat. The meat should lose its raw color and develop browned bits in the pot.
Pour off the excess grease. The pot should still look moist, but not oily.
Stir in the diced garlic and tomato sauce, then cook for 1 minute. The garlic should smell fragrant and the sauce should coat the beef evenly.
Add the chili powder, cumin, oregano, salt, and cayenne pepper, then stir well. The spices should bloom into the beef and give off a warm, savory aroma.
Lower the heat, cover the pot, and simmer for 1 hour, stirring now and then. By the end, the chili should look darker red and the aroma should be much richer.
Add 1/2 cup water if the mixture looks too dry after the simmer. You want it moist and spoonable, not scorched on the bottom.
Mix the masa harina with 1/2 cup water in a small bowl until smooth, then stir it into the chili. After a few minutes, the texture should loosen slightly, then turn thicker and silkier.
Adjust the consistency with more masa and or water if needed. The finished chili should be thick enough to mound on a spoon but still easy to ladle.
Stir in the drained and rinsed kidney beans and pinto beans, then simmer for 10 minutes. The beans should be hot through and the chili should look hearty and unified.
Serve warm with the garnishes you like best. A final squeeze of lime or a handful of cheddar wakes everything up nicely.