Spray a rimmed baking sheet with cooking spray. Set aside.

In a small bowl, combine baking soda, cinnamon, and nutmeg. Set aside.

Pour sugar and corn syrup into a large microwave-safe glass bowl. Stir using a sturdy spatula until well combined.

Microwave sugar mixture on high for 3 1/2 minutes, then stir. Return to microwave and cook for 3-5 more minutes until the mixture is a medium golden color. Check sugar mixture once each minute. Sugar scorches easily at this stage.

Remove bowl from microwave. Working quickly, add the vanilla, butter, and prepared spice mixture. Stir until combined. The candy mixture will bubble up and become airy.

Add the peanuts. Stir only enough to incorporate the peanuts with the candy mixture.

Working quickly, pour the brittle mixture onto the baking sheet. Use a silicone spatula or a spoon sprayed with cooking spray to press and spread the mixture out thinly. Alternatively, you can press and stretch the candy with your hands wearing heatproof food gloves.

Let the peanut brittle cool completely, about 1 hour. Break into pieces of your desired size (usually about 2 inches square). Store peanut brittle in an airtight container.