You'll need 7 ounces of peeled and roasted beets and 1/2 cup of water to make the beet puree. If you haven't already, add beets to a baking sheet and roast for 40-50 minutes in a preheated oven to 390ºF (200ºC), until fork tender. Simply blend the beets with the water using a food processor or an immersion blender, until you have a smooth paste. Then, on a clean surface, add 4 cups of flour and mix with 1/2 tsp salt. Make a well in the center and add the puree. Start mixing gradually until you have a dough bowl. Knead for 10-15 minutes, or until the dough is smooth and soft. Cover with plastic wrap and rest in the fridge for 30 minutes. Once ready, use a sharp knife or a bench scrapper to divide the dough ball into 8 pieces. Either using a pasta machine or a rolling pin, roll the dough as thin as you can without breaking it. Cut into your desired shape and cook as you would any fresh pasta.