Preparation Melt 6 tablespoons butter in medium skillet over medium-high heat. Whisk in brown sugar. Whisk until mixture bubbles thickly, about 2 minutes. Mix in cracker crumbs; stir 1 minute. Using back of fork, press warm crumb mixture over bottom and up sides of 9-inch-diameter tart pan with removable bottom. Cool crust completely. Pour milk into small custard cup. Sprinkle gelatin over. Let stand until gelatin softens, about 15 minutes. Whisk 1 cup sugar, lemon juice, and lemon peel in heavy medium saucepan to blend well. Whisk in eggs, then remaining 4 tablespoons butter. Whisk over medium heat until custard thickens and just begins to boil, about 5 minutes; remove from heat. Add gelatin mixture; whisk until gelatin dissolves. Let stand until beginning to set, about 10 minutes. Pour warm filling into crust. Chill until filling is firm, at least 3 hours and up to 1 day. Beat cream and remaining 1 tablespoon sugar in medium bowl until peaks form. Pipe or spoon cream over tart. Serve immediately or chill up to 4 hours.