Cream shortening, add sugar gradually, and beat until fluffy. Add eggs, one at a time, beating well after each addition. Beat in pawpaw puree. Sift together remaining dry ingredients and add in four portions, beating smooth each time.
Stir in nuts and raisins.
Pour batter into a greased, floured loaf pan (8x4x3-inches) and bake in a moderate oven (350 degrees) for about 50 minutes, or until a toothpick inserted into the loaf comes out clean. Cool on rack before slicing. Serve slices buttered or with cream cheese.
NOTE: To make puree, peel ripe pawpaws and place chunks in blender or food processor and process until smooth.