Preheat the oven to 350F. Line two baking sheets with parchment paper.
Combine the flour, baking powder, and salt in a medium bowl and mix together thoroughly.
In a large bowl with an electric mixer, beat the eggs and sugar for 3-4 minutes, until thick and pale. Gradually beat in the oil and the lemon zest.
Add the flour mixture, alternately with the milk, beginning and ending with the flour.
Scrape out the dough with a rubber spatula onto a clean counter. Spray hands with cooking spray (or rub on some olive oil)and divide the dough into 2 equal pieces. Shape each portion into a flattened logs that are about 3.5 inches wide.
Place the first logs one of the prepared baking sheets (if you’re using 1 baking sheet, space the logs out about 2-inches apart, they will expand a little while baking). Score the biscotti logs with a very sharp knife about 1/2-inch apart (this will help to slice them when they’re totally cooled down to prep for the second part of baking).
Bake until they are golden and firm, about 25 minutes, turning the tray halfway halfway through baking time. Cool on the sheet on a wire rack for 10 minutes.
Transfer sheet to a wire rack and let logs cool completely (could take a full 30 minutes). Reduce oven temperature to 325F degrees.
Transfer the first loaf carefully to a cutting board. When the logs have completely cooled down, begin slicing the first biscotti log approximately 1/2 inch apart by pressing a very sharp knife straight down into the dough (if you scored the dough, you’ll be slicing where you marked with the knife before baking).
Place the cookies back on the baking sheet, cut sides up. Keep in mind that the when you slice on a bigger angle, you will get much longer cookies. If you slice short angles, you’ll get small biscotti.
Place the second log on the cutting board and repeat process cutting out the cookie pieces and placing on the baking sheet. It should yield approximately 35-37 biscotti.
Bake 7 minutes, flip biscotti, and bake 7 minutes more (it may only take 5 minutes on each side, every oven is different). Let cool completely (they will also dry out a bit more) on wire rack. Enjoy!
For the Glaze
In a small bowl, stir together the lemon juice with the powdered sugar. It should become a thick and pourable glaze (if it’s too thick, add bit more lemon juice one teaspoon at a time. If it’s too confectioner’s sugar a tablespoon at a time).
Drizzle on the glaze and let it completely cool down. You could place the glaze in a zipped lock bag. Close the bag and cut a tiny triangle off a bottom corner of the bag. Gently squeeze the bag to add the glaze to the biscotti.