Preheat oven to 425F. Place first 6 ingredients (in order of ingredient list) in a food processor. Process for 20 seconds or until mixture resembles coarse sand. Transfer to a large bowl.
Whisk together egg and buttermilk; add to flour mixture, stirring just until dry ingredients are moistened and a dough forms. Turn dough out onto a lightly floured surface, and knead 3 to 4 times. Press dough on bottom and sides of a lightly greased 9-inch tart pan.
Bake at 425F for 20 to 22 minutes oruntil golden and firm to touch.
Microwave 1 Tbsp. marmalade at HIGH 10 seconds; brush over crust. Cool 45 minutes.
Stir together strawberries and 1/2 cup marmalade.
Beat heavy cream with 2 Tbsp. sugar at medium speed with an electric mixer until soft peaks form. Spoon onto cornmeal crust; top with strawberry mixture. Garnish, if desired.