In large bowl, combine butter and splenda blend. Beat until fluffy. Add egg, vanilla and milk. Beat thoroughly.
In another bowl, mix together flour, baking powder, and salt. Add splenda blend mixture to dry ingredients. Stir until mixed well.
Pour in a 9x13 greased pan. Spoon fruit evenly, within 1/2 inch from edges. Combine topping ingredients and evenly layer over fruit.
Bake uncovered in a preheated 350 degree oven for 45-50 minutes until the toothpick comes out clean. Let cool before serving.
WHEN USING FRESH RHUBARB: To tenderize it just put it in a saucepan with a little water and simmer it until it's just nicely pierced with fork. Do not sweeten it because the brown sugar topping will do that. I usually use frozen rhubarb that is room temp, but will use fresh in season. I'm going to try to freeze the rhubarb this year.