Pre-heat oven to 350 F
Grease a 9-inch square baking pan.
Combine flour, cinnamon, ginger, baking soda, and salt in a medium bowl.
In a mixer, cream butter and sugar on medium speed until light and fluffy.
Add molasses and eggs; beat well.
Add flour mixture alternately with milk, beating after each addition.
Pour batter evenly into prepared pan.
Bake 35 minutes, or until a toothpick inserted in center comes out clean.
Cool on a wire rack.
Top with lemon sauce and sprinkle with grated lemon peel.
Combine the sugar, butter, and cream in a small saucepan.
Cook over medium heat until butter is melted, stirring constantly.
Reduce heat to low, simmer for 5 minutes.
If desired, thicken with a little cornstarch slurry (1 tablespoon of cornstarch and 1 tablespoon of cold water...mixed)
Stir in lemon juice and lemon peel.
Pour over gingerbread cake!