Preheat oven to 400. Rub each beet with some olive oil and place on half of a sheet pan’s length of parchment paper. Add water and sprinkle beets with some salt and pepper.
Carefully fold the top half of the parchment paper over the beets. Starting with one side, roll and fold the edges the parchment so no liquid can escape and beets are completely enclosed. Continue folding until all edges are sealed.
Roast for 90 minutes. Remove from oven and be careful when opening parchment since steam inside is hot.
For the Tacos
Peel and discard beet skin. Dice into 1/2 inch cubes.
Saute onion and garlic in butter with the spices for 5 minutes until softened. Add beets (about 3 cups) and continue to saute for about 10 minutes until beets are browned and seasoned.
Fill Boston lettuce leaves with beet mixture and top with avocado, jalapeno, cilantro and any cheese you prefer. (I love using manchego)