Blend flour, almonds, sugar and salt in food processor. Add butter and cut in, using on/off turns, until mixture resembles coarse meal. Combine water and extract in samll bowl; pour over flour mixture and process just until moist clumps form. Gather dough into ball; flatten into disk. Press dough evenly over bottom and up sides of 9-inch diameter tart pan with removeable bottom. Freeze crust until firm, about 30 minutes. (Can be made 1 day ahead. Cover; keep frozen.).
Combine eggs and 1 1/4 cups sugar in heavy medium saucepan; whisk to blend. Mix in lemon juice and zest. Whisk over medium-high heat until mixture is thick and almost boils, about 5 minutes. Remove from heat; whisk in butter. Transfer filling to bowl. Chill until cold, stirring occasionally, about 2 hours. (Can be made 1 day ahead. Press plastic directly onto surface to keep skin from forming. Keep chilled.).
Preheat oven to 400°F Line crust with foil; fill with dried beans. Bake until sides are set, about 15 minutes. Remove foil and beans. Bake crust until golden, about 15 minutes. Cool completely. Reduce oven temperature to 350°F.
Spread filling in crust. Sprinkle almonds over. Bake until filling puffs slightly, begins to crack at edges and mos slightly in center when shaken, about 37 minutes. Cool completely on rack. Remove pan sides from tart. Sprinkle tart with powdered sugar and serve.