Preheat oven to 325°. Lightly spray an 8-inch round baking pan with cooking spray; line pan with parchment paper.
In a small heatproof bowl, stir together ¼ cup boiling water and baking soda until dissolved. Stir in molasses; set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and brown sugar at medium speed until creamy, 3 to 4 minutes, stopping to scrape down sides of bowl. Add egg, beating just until combined.
In a medium bowl, whisk together flour, ginger, cinnamon, salt, and cloves. With mixer at low speed, gradually add flour mixture to butter mixture alternately with molasses mixture, beginning and ending with flour mixture, beating just until combined after each addition. Stir in spiced rum and sour cream. Pour batter into prepared pan.
Bake until a wooden pick inserted in center comes out clean, 40 to 50 minutes. Let cool completely in pan. Garnish with confectioners’ sugar, if desired.
Recipe by Victoria at https://victoriamag.com/soft-gingerbread-cake/