Preheat oven to 350°.
To prepare sweet potato puree, place sweet potatoes in a stockpot, and cover with water; bring to a boil. Reduce heat, and simmer for 20 minutes or until tender. Drain potatoes; place in a large bowl. Add cranberries and next 7 ingredients (through eggs); beat with a mixer at high speed for 2 minutes or until smooth. Spoon sweet potato puree into a 13 x 9-inch baking dish coated with cooking spray.
To prepare streusel, combine pecans, brown sugar, flour, butter, and 1/4 teaspoon cinnamon. Sprinkle the streusel evenly over sweet potato puree. Bake at 350° for 30 minutes; remove from oven (do not turn oven off).
To prepare meringue, place the egg whites in a large bowl; beat with a mixer at high speed until soft peaks form using clean, dry beaters. Gradually add granulated sugar, 1 tablespoon at a time, beating until stiff peaks form (about 4 minutes). Spoon meringue into a pastry bag fitted with a star tip. Pipe meringue in a lattice design over streusel. Bake at 350° for 15 minutes or until lightly browned.