Arrange the rhubarb in a buttered baking dish and bake uncovered for 45 minutes, stirring occasionally. Add the strawberries and bake for 15 minutes longer. When done, transfer the fruit to a bowl and stir in the 6 tablespoons of granulated sugar. Set aside to cool.
When the fruit is cool, pre-heat the oven to 325 degrees F.
In a bowl, whisk the egg yolks and the 1/2 cup of granulated sugar to a ribbon stage. In a small saucepan, add the cream and split the vanilla bean, scrape out the seeds and add the pod and the seeds to the pan. Over moderately high heat, scald the cream and vanilla. In a stream, whisk into the egg yolk. Strain the custard into a pitcher.
Fill 8 ramekins halfway with the fruit and then cover with the custard. Place the ramekins in a roasting pan and pour enough hot water to reach halfway up the outside of each ramekin. Cover loosely with foil and bake for about 1 hour to 1 hour and 15 minutes or until custard is set. When finished, remove ramekins from the pan and cool on wire racks. Cool in the refrigerator until chilled, about 4 hours.
Just before service, cover each custard with the raw sugar and, using a torch, caramelize each dessert. If you don't have a torch, you can place them under the broiler. Serve and enjoy.