Place your butter in a small saucepan and melt over medium-low heat. Once melted, allow the butter to foam and sputter and then let it brown. This can take 5 minutes. The white milk solids should turn a light brown and it should smell nutty and toasted. Take off the heat.
Pour the browned butter in a bowl and let it cool. Place in the fridge for 2 hours until it firms up.
Whisk the flour, cinnamon, nutmeg, salt and baking soda in a medium bowl. Set aside.
In a stand mixer with the paddle attachment or using a hand held mixer, cream the softened browned butter for 2-3 minutes until it is very creamy.
Add your two sugars and beat for another 2 minutes.
Add the eggs and vanilla to the dough and mix for another minute. Make sure you scrape down the sides and bottom of the bowl to get all the dough mixed properly.
Add flour mixture to the butter and mix on a low setting until it is thoroughly combined. Fold in your oats and cranberries. The dough is going to be very sticky, so place in the fridge for at least 45 minutes.
Preheat your oven to 350°F/175°C and line 2 baking sheets with parchment paper.
Using a 3 tablespoon cookie scoop, scoop out the dough and make sure you have 3-4 inches between each cookie. Bake them 6 at a time on your cookie sheets for 13-14 minutes.
Allow the cookies to chill for 5 minutes before moving them to a cooling rack.