Preheat oven to 350 degrees. Separate stems and leaves from beetroot and allow to soak in cold water to clean. Rinse beetroot, thoroughly, and toss in 4 tablespoons of canola oil and 2 teaspoons of kosher salt. Place on roasting or saucepan and roast in a 350 degree oven for around 1- 1.5 hours or until the flesh is tender when pierced with a knife.
While beets are roasting, remove soaking beet greens and stems and finely chop. In a medium sauté pan, heat up the remainder of the canola oil (4 tablespoons) and cook beet greens with 1/2 of the minced garlic. Cook until greens are wilted and garlic is fragrant. Carefully remove greens to a plate reserving as much oil in the pan as possible. There will also be leftover liquid from the greens which is totally ok. To the pan add the sliced Spanish onion and cook on medium heat until deeply browned, about 15-20 minutes. Please stir frequently! When onions are browned, turn off heat and allow to cool.
Squeeze out liquid from cooked greens with your hands. Place greens, cucumber, red onion, and remainder of the minced garlic into a mixing bowl and stir in yogurt. Season to taste with additional salt and add pepper if you would like. Cover and refrigerate.
When beets are cooked, remove pan from the oven and allow beets to cool for at least 15 minutes. In a clean dish towel, roll around the warm beets (one at a time) until the skins come off. Place beet skins on a cutting board next to peeled beets.
Cut the beet skins into thin strips and place into saucepan with the caramelized onions. Turn the heat back on the saucepan to low and allow beet skins to crisp slightly.
Slice beets into thin wedges and arrange in the center of 4 plates. Sprinkle with kosher salt and squeeze 1/2 of a lemon over each plate of beets.
Remove beet green tzatziki out of refrigerator. Spoon a few dollops of the mixture onto the beets. Drizzle 1 tablespoon of olive oil on top of the tzatziki and then top with the crisped onions and beet skins. Repeat with the remaining 3 plates and then serve.
