Preheat oven to 400 degrees. Set rack in the center of the oven. Prepare the topping by placing all of the topping ingredients into a food processor. Pulse or mix until the mixture is crumbled to the size of small peas; do not over process. Set aside. Pour the rhubarb directly into a large, shallow baking dish and sprinkle with 1/2 cup plus 2 tablespoons sugar and 3 tablespoons of flour to coat evenly. Spread crisp topping over entire surface. Bake until fruit is bubbly and the top is golden brown, approximately 30 to 40 minutes. Serve warm or room temperature, plain or a la mode.