Preheat oven to 325°F. Spray two jumbo muffin tins (or a mini cakes tin) with baking spray or grease with butter and dust lightly with flour, shaking out excess. Line each tine with a slice of lemon and top with an even coating of caramel (or brown) sugar (this is optional).
In your mixer, using the paddle attachment, cream the butter and sugar together until light and fluffy- about 7 minutes.Scrape down the bowl and paddle occasionally.
During the mixing, sift together the dry ingredients 3 times. Set aside.
Add the lemon zest and vanilla to the butter-sugar mixture. Mix to combine. Scrape down the bowl before adding the first of your eggs.
Continue adding the eggs, one at a time and scraping the bowl down after mixing in each egg. Mix for an additional 3 minutes. Scrape down your bowl,
Mix the dry ingredients into the mixing bowl in 2 parts, alternating with the sour cream. Scrape down your bowl after each addition.
Divide your batter into your tins evenly. Bake in your preheated oven for 30-35 minutes, or until the centers spring back when lightly pressed. Remove from the oven and allow to cool for 5 minutes before turning out onto a baking rack to cool completely. While they are cooling prepare your syrup.