Preheat the oven to 350°F (180°C). Line two baking sheets with parchment paper.
In a medium-sized bowl, whisk together the flour, baking powder, cornstarch, and salt. Set aside.
In a large bowl, mix together the sugar with lemon zest until fragrant. Add the egg and oil and mix to combine. Add the vanilla extract and lemon juice and mix again until incorporated.
Gradually incorporate the flour mixture and fold in chocolate chips or chunks and the chopped strawberries. Don't overmix.
Using an ice cream scoop, take equal portions of dough and place them on the prepared baking sheets, 1 inch (2.5 cm) apart.
Sprinkle each with granulated sugar.
Bake for 10-12 minutes until slightly golden on the edges.
Let the cookies cool on the baking sheets until the cookies are firm enough to remove, probably another 5 minutes. Cool completely on a wire rack. Enjoy!