In a large bowl, mix the salt and sugars together with a whisk. Make sure there are no clumps. Add the maple syrup and whisk well, add it to the sugars, stir. Add eggs and vanilla extract whisking until just combined. In a small saucepan, melt the butter over medium to low heat. Stir in the 1 tablespoon flour and cook for about 30-40 seconds whisking vigorously. Add to the egg mixture, stirring well with the whisk.