Preheat your oven to 350°F (175°C).
In a small bowl, soak the raisins in hot water for about 10 minutes, then drain and set aside.
In a large mixing bowl, whisk together the all-purpose flour, ground cinnamon, baking soda, and fine sea salt.
In another bowl, beat the unsalted butter with light brown sugar and granulated sugar until light and fluffy, about 3-4 minutes.
Add the egg and vanilla extract to the butter-sugar mixture, mixing until well combined.
Gradually add the dry ingredients to the wet mixture, stirring gently until just incorporated.
Fold in the old-fashioned oats and the plumped raisins using a rubber spatula.
Scoop the dough onto the prepared baking sheet, leaving about 2 inches of space between each cookie. Bake for 10-12 minutes or until the edges are golden.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a cooling rack.
