Warm the oven to 375 degrees and lightly grease a large baking sheet.
Add the spinach and onion to a food processor and pulse until small. Add the kidney beans, rice, garlic, liquid smoke, soy sauce, and seasonings and pulse until combined. Place the bean-spinach mixture into a medium bowl and add the breadcrumbs. This should be slightly sticky and hold nicely when you form it into a ball. If it is too wet, add more breadcrumbs.
Divide the mixture into 16 patties if you are making sliders or 8 patties if you are making regular burgers. Place them on the baking sheet, spray them lightly with oil. Bake for 15 minutes or until the bottom is a crispy golden brown. Flip the patties and bake for 15 or until both sides are crisp. If you are doing full size burgers you might need to let the sides go 5 extra minutes. Let them cool for a few minutes before serving. Pile them high with red onion, avocado, whatever additional deliciousness you’ve got.