On a baking sheet, toss diced onion and sweet potato with cumin, paprika, 1 tablespoon olive oil, 1⁄2 teaspoon kosher salt, and pepper. Arrange in a single layer, transfer to oven, and roast until tender, 12-15 minutes.

While vegetables roast, place quinoa, 1⁄2 cup water, and a pinch salt in a small pot over high heat. Bring to a boil, then reduce heat to medium and simmer until water is evaporated and quinoa is tender, 10-12 minutes. Remove pot from heat and set aside.

In a large bowl, stir together green cabbage, red cabbage, carrots, apple cider vinegar, honey, sliced onion, spinach, and 1 tablespoon olive oil. Season with 1⁄2 teaspoon kosher salt and pepper as desired. Halve avocado and discard pit. Using a spoon, carefully scoop out flesh and place in a medium bowl, discarding skin. Add juice of 1 lime. Using a fork, mash until mostly smooth. Season with 1⁄4 teaspoon kosher salt and pepper as desired.

In a large bowl, combine roasted sweet potato-onion mixture and black beans. Using a potato masher or fork, gently mash until mostly smooth. Add quinoa and using your hands, mix well (see Recipe Tip). Divide mixture evenly and form into 2 patties, about 1⁄2-inch thick. Heat 1 tablespoon olive oil in a large nonstick pan over medium-high heat. When oil is shimmering, add burgers and sear until lightly browned, about 3 minutes per side. Transfer to a plate.

Wipe pan from burgers clean. Halve buns and add to pan over medium heat. Toast until until lightly golden, 1-2 minutes per side. Top bun bottoms with burgers, dividing evenly. Slather avocado mash on top, then add 1-2 tablespoons slaw. Finish with bun tops and enjoy with remaining slaw alongside.

CAKE