Preheat oven to 380°F. Line a cupcake tin with cupcake liners or spray with non stick baking spray.
Make the streusel topping first: combine the flour, brown sugar, almonds (optional) and lemon zest in a medium sized bowl. Add the pieces of cold butter into the bowl and use a pastry blender or fork to cut the butter into the mixture until it is the texture of coarse meal. You do not want it to become a cohesive dough. Set aside.
In a large bowl, whisk the flour, sugar, poppyseeds, baking powder, baking soda, salt, lemon zest and cardamom together.
In a separate bowl, whisk the milk, butter, eggs, lemon juice and lemon extract together until smooth. Gently fold in this mixture into the flour mixture until just combined. It will be very light and fluffy & it's OK if it's not all mixed.
Use a 1/4 cup measuring cup to scoop batter into each cupcake tin. Then top each muffin with about ~1 Tbsp. streusel topping. Place in oven and immediately turn the oven to 400°F (this helps ensure a dome on your muffins instead of flat muffin tops!) Bake for 13-15 minutes or until you insert a toothpick and it comes out clean. Enjoy!