In a heavy saucepan, or double boiler, combine the egg whites, cream of tartar and remaining sugar and water; beat on low speed with portable mixer for 1 minute. Continue beating over low heat until mixture reaches 160^, about 10 minutes. Remove from heat. Add vanilla; beat until stiff peaks form, about 4 minutes. Spread meringue over frozen ice cream cake, sealing meringue to the platter, sprinkle with almonds.