Preheat the oven to 350°F. Line baking sheets with parchment paper.

In a medium bowl, whisk oats, flour, salt, baking powder, cornstarch, and cinnamon.

In a large bowl, cream butter and brown sugar until light and fluffy. Add molasses, egg, and vanilla extract; beat until combined.

Gradually add dry ingredients to the butter mixture; stir in the raisins.

Drop dough onto baking sheets using a large cookie scoop or ¼ cup measuring cup.  With a heavy bottomed glass, gently press the top of each cookie down. Bake for 14-16 minutes.

Cool on a baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

Store the Molasses Oatmeal Raisin Cookies in an airtight container at room temperature for up to a week.