Mix the almond flour, poppy seeds, baking powder, salt and the zest of a lemon in a bowl and mix together with a fork.
In another bowl cream together the butter and sweetener. Avoid using a granulated sweetener (unless you are not on Keto and using sugar) but otherwise they are hard to dissolve and it's better to powder them.
Then add the sour cream to the butter and sweetener mixture and whisk together.
Then add in the vanilla, eggs and lemon juice and whisk in together. Don't be alarmed if the mixture looks a bit curdled or split, this is normal.
Finally add in the dry ingredients to the wet and whisk till you get a nice smooth batter.
Pour the batter into cupcake/muffin liners and then bake for about 25-30minutes at 175C. Don't forget to preheat your oven.
Once ready, let them cool for 20 minutes at least before digging in.