1. Preheat oven to 400°.
2. Sift together flour and baking powder in a medium bowl. Stir in cornmeal and salt until blended.
3. Cream together butter and sugar in a separate bowl at medium-high speed with an electric mixer until light and fluffy; beat in egg. Add dry ingredients to butter mixture alternately with milk, scraping bowl several times, until well blended. Gently fold in cranberries.
4. Spoon into greased or lined muffin pans, filling two-thirds full.
5. Bake at 400° for 20 to 22 minutes until muffins are set and just starting to turn light golden brown.
6. Cool in pans 2 minutes; turn out, and cool on wire rack for 3 to 5 more minutes. Serve warm.