Around these parts, if you walk your dog during the middle of the day you'll burn its feet as the sidewalks are so hot. Advancing on that theory and on the fact you can cook an egg on the sidewalk, which I have done, I created the solar oven last summer, which was really a cardboard box lined with aluminum foil, with one end open to let in the sunlight. I cooked a baked potato, although it took four hours.
So, this winter I've been thinking about how to improve my design. I've got some ideas and plans to try some other things and see how they'll cook with nothing but the sun for energy. First, it has to warm up a little. Stay tuned.