Slice the mangoes into 3/4-inch pieces; transfer to a medium bowl. Stir in the lemon juice, 3 tablespoons sugar, and 1 tablespoons flour and set aside.
In a medium bowl, whisk together hazenuts, salt, remaining 3/4 cup flour, and 1/3 cup sugar until combined. Cut in butter with a pastry cutter or two knives, until the mixture is crumbly. Continue working in the butter until completely incorporated and there are no dry crumbs. Squeeze mixture together to create pea-size to half-inch clumps.
Add the raspberries to the reserved mangoes, and divide the mixture among 4 small baking dishes. Place one-quarter of the nut and flour mixture on top of each baking dish, allowing some of the fruit to show through. Bake until golden brown and the fruit juices are thick and bubbling 35-40 minutes. Remove from oven; place on wire rack until slightly warm.