Wash beets, wrap in foil and bake in the oven until soft (about 1 hour) to Cool, to clean, to grate on a fine grater (or punch in the processor), mix with grated ginger, juice and zest of lemon. Cover with sugar, mix well. Bring to a boil in a saucepan, and cook stirring for 5 minutes. To put into jars, cool and store in the refrigerator for months. If you want to store longer, it should perform the normal procedure to sterilize jars and lids, fill with hot marmalade to sterilized again in boiling water and roll.