Preheat oven to 325°F / 160°C.
Slice strawberries in half, removing their tops.
In a small bowl whisk eggs and vanilla extract together. Set aside.
In a measuring cup, combine coconut sugar, baking soda, salt, and fennel seeds. Measure out the nut butter and place in a large bowl. Add the egg mixture, stir thoroughly to combine. Add the coconut sugar mixture and fold together. The dough will be very thick.
Press the dough into a lightly-greased 8" / 20cm square pan. Press the strawberries in to the top. Sprinkle with a pinch of flaky sea salt and place in the oven.
Bake for 25-30 minutes until the blondies are golden brown. Remove from the oven and let cool in the pan completely before cutting.