- 1 sheet frozen puff pastry (from a 17 1/4-oz package), thawed
- 1 pound rhubarb stalks, trimmed and cut crosswise into 1-inch pieces
- 1/2 cup confectioners' sugar
- 1 (10 ounce) package frozen strawberries in heavy syrup, thawed
- 3/4 cup creme fraiche or sour cream
- Bake pastry: Preheat oven to 425 degrees F.
- Unfold puff pastry sheet and gently roll out with a floured rolling pin on a very lightly floured surface into a 12-inch square. Trim edges with a sharp knife, then cut pastry into 6 rectangles (about 6 by 4 inches each). Arrange rectangles 1 to 2 inches apart on an ungreased baking sheet and prick them all over with a fork.
- Bake in middle of oven until pastry is puffed and golden, 13 to 15 minutes. Cool pastry on baking sheet on a rack.
- Roast rhubarb while pastry is cooling: Reduce oven temperature to 375 degrees F.
- Arrange rhubarb in 1 layer in a lightly oiled shallow 15- by 10-inch baking pan (preferably nonstick) and sift 2 tablespoons confectioners sugar evenly over it. Roast in middle of oven until tender, 15 to 25 minutes, then cool in pan on a rack.
- Make strawberry sauce and cream filling while rhubarb is roasting: Puree strawberries with syrup in a food processor, then force puree through a very fine sieve into a bowl.
- Sift 5 tablespoons confectioners sugar over creme fraiche and whisk to combine.
- Assemble tarts: Sift remaining tablespoon confectioners sugar over pastry rectangles. Make a 3-inch lengthwise trough in the center of each rectangle by gently tapping with back of a teaspoon. Divide cream filling among troughs and top with rhubarb, then drizzle with strawberry sauce.