Place your strawberries, rhubarb, and 1/2 cup of the sugar in a medium saucepan, cover, and let simmer until the fruit is soft, stirring frequently. Keep it simmering until ready to use.
In a large bowl, blend the flour, remaining sugar, baking powder, cinnamon, and salt. Stir in the milk.
Preheat the oven to 350 degrees. Melt the butter in the microwave, then pour it into a 9X11 glass baking dish. Swirl it around to coat the entire bottom of the dish.
Pour the batter over the butter.
Spoon the hot fruit over the batter, trying to keep it relatively even. Don't stir it in!
Bake at 350 degrees for approximately an hour. To check if it's done, use a fork to lift up a bit from the middle. The cake portion should be fluffy and done, while the fruit and cake which touches the fruit will remain slightly gooey.
Let the cobbler cool for about 10 minutes before serving. It's wonderful served with a dollop of ice cream or whipped cream.