In large mixing bowl, stir together flour, salt, and baking powder. Set aside.
In mixer or another large mixing bowl, combine butter and sugar until creamy. Add eggs, one at a time. Beating well after each addition. Add lemon and vanilla extract and stir to combine.
Add flour and buttermilk alternately to sugar/butter mixture. Starting and ending with flour mixture. Mix until well combined.
Transfer batter to well greased and floured baking pan. Bake at 325 for 90 minutes.
While cake is baking, make glaze by combining maple syrup and powdered sugar. Stir until smooth. Set aside.
Remove cake from oven and let cool 10 minutes. Remove cake and add glaze by spooning it over top of cake. Decorate as desired with lemon slices. Let cake cool completely before serving.