Preparation Preheat oven to 350°F with rack in middle. Butter and flour a 9-inch cake pan, knocking out excess. Whisk together flour, baking soda, cinnamon, allspice, and salt. Melt butter with water. Beat together brown sugar and molasses with an electric mixer until combined. Add eggs 1 at a time, beating well. Beat in flour mixture at low speed until just combined. Add butter mixture and ginger, beating just until smooth. Pour into cake pan. Peel pear and cut into 3/4-inch pieces. Scatter over batter. Bake until a wooden pick inserted into center comes out clean, about 35 minutes. Cool slightly.
Preparation Preheat oven to 350°F with rack in middle. Butter and flour a 9-inch cake pan, knocking out excess. Whisk together flour, baking soda, cinnamon, allspice, and salt. Melt butter with water. Beat together brown sugar and molasses with an electric mixer until combined. Add eggs 1 at a time, beating well. Beat in flour mixture at low speed until just combined. Add butter mixture and ginger, beating just until smooth. Pour into cake pan. Peel pear and cut into 3/4-inch pieces. Scatter over batter. Bake until a wooden pick inserted into center comes out clean, about 35 minutes. Cool slightly.