Preheat oven to 375 degrees F. Grease a 12-inch pizza pan; set aside. For crust: In a large bowl, beat shortening with an electric mixer on medium to high speed for 30 seconds. Add sugar, baking powder, ginger, baking soda, cinnamon, and cloves. Beat until combined, scraping side of bowl occasionally. Beat in molasses, egg, and vinegar until combined. Beat in as much of the flour as you can with the mixer. Using a wooden spoon, stir in any remaining flour.
Press dough into the prepared pan, building up edge slightly. Crimp edge as desired. Bake about 12 minutes or until edge is lightly browned and center appears set. Cool in pan on a wire rack.
Stir cream cheese to soften. Spread cream cheese over crust. Carefully brush melted marmalade over cream cheese. Brush pear slices with lemon juice. Arrange pear slices in a decorative pattern on top of tart. Cover and chill for 1 to 4 hours. Makes 12 servings.