No need to preheat the oven yet, the dough needs to chill. Make the cookie dough first: Place the butter and sugar into a large bowl, or the bowl of your stand mixer and beat on medium-high speed until light and fluffy. This takes around 2 minutes.
Add in the egg and vanilla extract, scraping down the sides as necessary. Mix on medium speed until everything is smooth and incorporated, around 1 minute.
Add in the pumpkin purée, flour, cream of tartar, bicarbonate of soda, salt, pumpkin pie spice and ground cinnamon. Mix on low until the mixture starts to come together, then turn up to high and mix until a soft dough forms. Dough will be softer and a bit stickier than a normal cookie dough. This is how it's supposed to be.
Cover the bowl of dough with cling film and place in the fridge for 45 minutes to chill.
Once the dough has chilled, preheat the oven to 180C/350F and line 2 baking trays with grease proof paper/a silicone mat. Unwrap your soft caramels and leave on the wrapping it comes in to one side.
Make the cinnamon sugar: In a small bowl, mix together the granulated sugar and cinnamon until well combined and there are no lumps of cinnamon.
To make the cookies (I like to wear gloves for this bit as it can get messy!) - Using a 2tbsp cookie scoop, scoop a ball of dough up, transfer it to your palm and flatten it a bit. You want it to be around 1/2 inch thick. Place your caramel in the centre, then bring up each site to cover the caramel. Roll between your palms to make a ball of dough then roll in cinnamon sugar. Place on baking tray and repeat. Leave a 2 inch gap between each Snickerdoodle.
Place in the oven for 9-11 minutes until the top looks matte and feels slightly crisp to the touch. They will look soft still, this is fine, they'll set while cooling.
Leave cookies to cool at least 10 mins before tucking in if you must! I love warm cookies from the oven! Otherwise leave to cool completely on the baking trays before storing in an airtight container for 5 days.
You can serve these Caramel Stuffed Pumpkin Snickerdoodles at room temperature or warmed slightly in the microwave. The caramel will stay soft at room temp, but goes gooey when reheated.