Easy Frittata with Smoked Salmon



½ leek, finely sliced
1 small sweet potato, peeled and finely sliced
½ cup zucchini, grated
5 eggs
½ cup sour cream
⅓ cup grated fresh parmesan cheese plus 1 Tbsp extra
Salt and pepper
1Tbsp chopped dill, plus extra for garnishing
200g smoked salmon
½ lemon