PreparationFor topping: Whisk flour, golden brown sugar, lemon peel, and salt in medium bowl to blend. Add melted butter and vanilla; stir until evenly moistened but crumbly. DO AHEAD: Can be made 4 hours ahead. Let stand at room temperature. For filling: Whisk eggs in large bowl to blend. Whisk in crème fraîche and vanilla. Add 1 tablespoon flour; whisk to blend. do ahead Can be made 4 hours ahead. Cover and chill. Rewhisk before continuing. Preheat oven to 375°F. Butter 8x10- inch oval ceramic dish. Place berries and nectarines in large bowl. Sprinkle remaining 1/2 cup flour and sugar over; toss to coat. Transfer to prepared dish. Pour egg mixture evenly over fruit. Using fingers, crumble topping over fruit, distributing evenly. Bake crisp until custard is set and topping is golden brown, about 55 minutes. Let cool at least 10 minutes and up to 1 hour before serving. Scoop crisp into bowls. Serve with vanilla ice cream.
PreparationFor topping: Whisk flour, golden brown sugar, lemon peel, and salt in medium bowl to blend. Add melted butter and vanilla; stir until evenly moistened but crumbly. DO AHEAD: Can be made 4 hours ahead. Let stand at room temperature. For filling: Whisk eggs in large bowl to blend. Whisk in crème fraîche and vanilla. Add 1 tablespoon flour; whisk to blend. do ahead Can be made 4 hours ahead. Cover and chill. Rewhisk before continuing. Preheat oven to 375°F. Butter 8x10- inch oval ceramic dish. Place berries and nectarines in large bowl. Sprinkle remaining 1/2 cup flour and sugar over; toss to coat. Transfer to prepared dish. Pour egg mixture evenly over fruit. Using fingers, crumble topping over fruit, distributing evenly. Bake crisp until custard is set and topping is golden brown, about 55 minutes. Let cool at least 10 minutes and up to 1 hour before serving. Scoop crisp into bowls. Serve with vanilla ice cream.