Preheat oven to 225. Line a baking sheet with brown paper or parchment. Beat egg whites and cream of tartar in a small bowl with an electric mixer at high speed until soft peaks form. Gradually beat in sugar and vanilla, and continue beating until stiff and glossy, but not dry. Spoon onto paper to form a 9-inch circle, slightly indenting center. Place in middle of oven. Bake for 1 1/2 hours; turn off oven and, leaving door closed, let stand in oven 1 hour longer. Remove from oven. Using a long knife, gently release from paper and cool on a wire rack. (If meringue sticks to paper, place paper on top of a damp terry cloth towel for 1 minute to release.) Beat cream and powdered sugar in a small bowl with an electric mixer at medium speed until stiff peaks form. Frost top and sides of Pavlova with cream and top with fruit. Cut into wedges to serve. Refrigerate leftovers.