When I was a kid, with the robust rhubarb, we frequently made it into a crisp. The main thing I remember is the shocking contrast between the crunchy/sweet topping and the mushy/sour rhubarb. I was fairly sure the sweetener was white sugar, and most crisp recipes call for brown sugar.
The recipe was lost, though, and I've been trying to recreate it for years. I'd tried a few white-sugar toppings, and they never came out the way I remembered, but were more like soft sugar cookies, rather than crunchy bits.
Apparently, I forgot to check my standard resource: The Joy of Cooking. That recipe calls for brown sugar too, but substituting white sugar produced exactly the result I remembered from childhood.
I made the recipe both ways (shown in the August 2 picture), and held a tasting. The majority opinion (okay, so I was the only hold-out among the five of us, so it was probably more about nostalgia than tastiness) concluded the brown sugar was better.
Take 4 cups of rhubarb, cut into pieces and slightly sweetened with a tablespoon of honey, and spread in a pie pan. Sprinkle with a few bits of lemon zest and a tablespoon or two of lemon juice.
For the topping, cream 1/4 cup of butter with 1/4 cup of sugar (brown or white), and then mix in 1/2 cup of flour. Stop mixing when it's crumbly, and then toss on top of the fruit. Bake at 350 to 375 degrees for about half an hour.