Cream softened butter with the paddle attachment of your stand mixer or beat well with your hand mixer until the butter has lightened in color, about 3 minutes.
Add confectioner's sugar and incorporate fully. Turn your mixer onto high speed to make sure the sugar is well incorporated and to lighten the mixture. Reduce the speed of your mixer and add maple syrup, vanilla extract, and salt.
Turn your mixer back onto high speed and beat for about 30 seconds to lighten. Taste the buttercream to make sure it has the flavor you prefer, if you would like more maple flavor, add maple flavoring 1 teaspoon at a time until it has reached the flavor you prefer. You may need to incorporate additional sugar to have your buttercream at the proper consistency.