In small mixing bowl, beat egg whites with cream of tartar at high speed until foamy. Add sugar, 1 tablespoon at a time, beating constantly until sugar is dissolved and whites are glossy and stand in soft peaks. (Rub just a bit of meringue between thumb and forefinger to feel if sugar has dissolved.) Beat in vanilla.

Spread meringue over hot pie filling, starting with small amounts at edges and sealing to crust all around. Cover pie with remaining meringue, spreading evenly in attractive swirls. Bake in preheated 350°F oven until peaks are lightly browned, about 12 to 15 minutes. Cool at room temperature. Refrigerate until serving.

MICROWAVE: Prepare meringue and cover pie as above. Cook on full power, rotating 1/4 turn every minute, until knife inserted horizontally into side comes out clean, about 3 to 3 1/2 minutes.

TO POACH: Drop meringue mixture by spoonfuls onto simmering milk or water. Simmer, uncovered, until firm, about 5 minutes. Smaller spoonsful will not need to be turned over, but large ones may require turning halfway through the cooking time. With slotted spoon, remove meringues from milk and drain on paper towels. Serve or chill until ready to serve.

Note: All microwave cooking times are based on a full power output of 600 to 700 Watts. For a lower wattage oven allow more time.