Preheat the oven to 180° C/356° F with convection setting.
Place a colander over a bowl, add the watermelon, and, wearing disposable gloves, crush it with your hands to break it into pieces. Strain the liquid into another bowl.
Add the flour, sugar, walnuts, honey, and cinnamon. Mix with your hands until the dough is uniform.
Spray a 35x25 cm (~14x10-inch) rectangular baking dish with olive oil and evenly sprinkle half the sesame seeds on the bottom ensuring it is completely covered.
Spread the pie dough evenly over the entire surface of the dish, covering the sesame seeds. Press it with your hands, sprinkle with the remaining sesame seeds, and bake for 40-45 minutes.
Remove the watermelon pie from the oven, cut into pieces and serve.