Preheat oven to 350 F degrees. Using pencil and ruler, draw a 10 1/2 X 4 inch rectangle on a piece of kitchen parchment. Spray kitchen parchment with vegetable oil spray on unmarked side and place pencil side down on baking sheet.
In a bowl add the semolina flour, all-purpose flour salt and baking powder. Whisk to thoroughly combine.
In a food processor mix eggs until lightened in color and almost double in volume, about 3 minutes. With processor running, slowly add sugar until combined, about 15 seconds. Add melted butter and vanilla extract and process until combined, about 10 seconds. Transfer egg mixture to medium bowl. Sprinkle half of the flour mixture over egg mixture and, using spatula, gently fold until just combined. Add remaining flour mixture then the pineapple, coconut and nuts. Gently fold until combined.
Using floured hands, form the dough into a 10 1/2 X 4 inch rectangle using the penciled lines a s a guide. Spray the loaf lightly with oil spray. Using rubber spatula that is lightly coated with oil spray, smooth tops and sides of the rectangle. Using a sharp knife coated with oil spray, cut the loaf in half making it into two -- 2 X 10 1/2 inch loaves. Separate loaves leaving 2 inches between them. Here we put a 4 X 14 inch strip of oiled parchment in-between the loaves, tucking the oiled strip under the cut loaves and leaving the 2 inch gap between the loaves. Bake until loaves are golden and just beginning to crack on top, 25 to 30 minutes, rotating pan halfway through baking.
Remove from oven and let cool on baking sheet for 25 minutes. Transfer loaves to cutting board. Gently mist water on top of loaf and on a serrated knife. Slice each loaf on a slight diagonal into 3/4 inch-thick-slices. Lay slices, cut side down, about 1/4 inches apart on a wire rack set in a rimmed baking sheet. Bake until crisp and lightly golden, about 35 minutes. Let cool completely before serving. Biscotti can b stored in an airtight container for up to 1 month or frozen until ready to serve.