Preheat the oven to 350°F. Grease and line a 9X13-inch baking pan with parchment paper, leaving some paper overhang for easy lifting. Set aside.
Sift Flour, baking powder, soda, and salt and set aside.
3 cups Cake & Pastry flour, 1 tablespoon Baking powder, ½ teaspoon Baking soda, ½ teaspoon Salt
Use the paddle attachment to cream the butter and sugar for a few minutes.
½ cup Butter, 2 cups Sugar
Add the oil and keep mixing. Scrape the bottom and sides of the bowl in the meantime.
½ cup Oil
Add the eggs, one at a time and beat well after each. Add vanilla extract, strawberry extract, and pink colour if using.
4 Eggs, 1 tablespoon Vanilla extract, 1 teaspoon Strawberry extract
Add the strawberry reduction and gently mix.
1 cup Strawberry reduction
Add ⅓ of the dry ingredients alternating with ⅓ of milk. Repeat until all the dry ingredients and milk are used, starting and ending with dry ingredients. Use a rubber spatula to incorporate all ingredients.
1 cup Milk
Pour the batter into the prepared pan, and bake for 30-35 minutes, until the top is golden and an insert comes out clean. Let the Strawberry Sheet Cake cool in the pan for 15 minutes, flip it on a cooling rack and let it cool completely before frosting.