Cut butter into flour until crumbly. Stir in pecans. Press into an ungreased 13-in. x 9-in. baking dish. Bake at 350° for 15 minutes. Cool. In a small bowl, beat cream cheese and confectioners' sugar until fluffy. Fold in whipped topping. Spread over crust; chill.
In a small saucepan, combine the sugar, cornstarch and salt. Stir in water until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer.
Remove from the heat.
Stir a small amount of hot filling into eggs; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Remove from the heat; gently stir in the vinegar, lemon juice, butter and extract. Cool to room temperature without stirring. Spread over cream cheese layer. Refrigerate for 2 hours or overnight.