Step 1

Whisk mascarpone cheese, honey, and lemon juice in small bowl to blend. Cover; chill until ready to serve. (Can be made 1 day ahead; keep chilled.)

Step 2

Preheat oven to 350°F. Butter and flour 8-inch square metal baking pan. Whisk first 6 ingredients in medium bowl to blend well; whisk in crystallized ginger. Whisk oil, molasses, and brown sugar in large bowl to blend; whisk in egg and lemon peel. Gradually whisk in dry ingredients, then boiling water. Transfer batter to prepared pan.

Step 3

Bake cake until tester inserted into center comes out clean, about 30 minutes. Cool cake 15 minutes. (Can be made 1 day ahead. Cool completely; cover and store at room temperature.) Cut cake into squares; sift powdered sugar over. Serve warm or at room temperature with topping.

Step 4

Italian cream cheese available at Italian markets and many supermarkets.