Preheat oven to 350℉. I used a silicone regular muffin tray but if you're using a metal one, make sure to grease with butter or spray with avocado oil.
In a large bowl, whisk together the almond flour, sugar and salt. Next, add in the egg whites, lemon zest, vanilla extract, almond extract and mix together until incorporated (you might have to use your hands to fully incorporate).
Next scoop 2 tablespoons of the cookie dough into each muffin slot and press gently down and up towards the sides. Add 1 teaspoon of jam to each cookie. Then add 1 tablespoon of dough and gently press down to cover the jam. (You can also add some turbinado sugar to the tops here for aesthetic if you like - I didn't). Bake for 15 minutes at 350℉ and then 3 more minutes at 425℉ to give a golden color on top.
Store leftovers in an airtight container on your counter up to 5 days.
If you don't have strawberry preserves, you can use any other type of jam you have like raspberry, blueberry, fig, apricot or cherry.
If you don’t have caster sugar, you can make your own by running regular sugar through your mini food processor to make the texture finer. You can also skip the step and just use straight up granulated sugar. The recipe will still be delicious!