Wash the lemons and pat them dry. Use a fine grater or zester on the lemon rind, careful not to "zest the white" part, only the rind. Combine the ingredients in a quart mason jar and shake it every day for 30 days. Then strain the lemon zest into a clean jar with an airtight lid. This extract will keep for 3-4 years if kept in a cool dark place. Refrigeration is not needed.