Step 1: In a large mixing bowl, place the butter and maple sugar. Mix together using a fork or a hand mixer until well combined. 

Step 2: Prepare the flax egg: In a small bowl, stir together the 1 tablespoon golden flaxseed meal and 3 tablespoons water. Mix and set aside. It will thicken after 10 minutes or so.  To the butter and sugar, add the flax egg, pumpkin purée and vanilla extract. Mix well. 

Step 3: Prepare a sifter then add the flour, baking soda and sea salt. Sift together into a large mixing bowl. Combine the wet and dry ingredients. Mix well until a dough forms. Gather the dough together and make a flat disk. Cover it with wax paper or plastic wrap. Refrigerate overnight or at least 6 hours. 

Step 4: Preheat the oven to 350 degrees F. Prepare the sugar topping by placing the sugar in a small bowl and adding a few drops of the red natural food coloring. Mix until the color is evenly distributed. 

Step 5: Remove the dough from the refrigerator and unwrap it. Place it on a lightly floured board. Roll it out very thinly, or about ⅛ of an inch-thick. Using a heart-shaped cookie cutter, cut out heart shapes. Use a spatula to carefully transfer the cookie shapes to a baking sheet. Top each cookie with a sprinkle of colored sugar. Bake at 350 degrees Farenheit for 7 to 8 minutes, checking the bottoms to avoid overbrowning. Transfer to a cooling rack and cool completely. The cookies will crisp up as they cool. Once completely cool, serve or store in a cookie tin.