Preheat the oven to 200C fan-forced, grease and line a baking tray with baking paper.
Arrange kumara and patties across baking tray, and drizzle with oil. Bake, turning patties halfway, for 18-20 minutes or until both are cooked through.
Meanwhile, for the quickles, place everything in a saucepan over high heat. Bring to the boil then cover and cook for 5 minutes or until softened slightly. Remove from heat and stand covered until required.
Combine sour cream and cheese in a bowl and mix to combine. Divide between bun bottoms. Bake for 4-5 minutes or until cheese sauce is melted and oozing.
Toss spinach, dill, apple and lemon juice in a bowl.
To assemble burgers. Top bun bottoms with kumara wedges, meat patties, quickled beetroot and tossed salad. Spread mayo across bun tops and top to finish.