In a large bowl, using a hand held mixer, beat butter and sugar until light and fluffy. Add egg. Beat 1 minute. Gradually beat in juice. Add flour, baking powder, orange zest, and salt. Mix until just blended. Stir in cranberries and toasted walnuts. Spread batter into pan.
Bake until top of loaf is golden and a toothpick inserted in
center comes out clean, 50 to 55 minutes. Let stand in pan for 10 minutes, then
unmold onto a wire rack and let cool completely.