Heat the olive oil in a large, deep frying pan over a medium heat. Add the sliced leek and cook for 8 minutes, stirring regularly, until softened.
Add the minced garlic and cook for a further 2 minutes.
Add the rice and stir to coat it in the olive oil. Add the vegetable stock, tomato purée, baby spinach, half of the dill, half of the parsley and half of the lemon zest. Season with salt and pepper.
Bring to a gentle simmer, then reduce the heat to low and cover with a lid. Cook for 20–25 minutes, or until the rice is tender and has absorbed most of the stock.
Remove from the heat and leave to rest, covered, for 2 minutes.
Stir through the remaining dill, parsley and lemon zest, followed by the lemon juice.
Taste and adjust the seasoning, adding extra lemon juice, salt or pepper as required.
Scatter over the vegan feta and toasted pine nuts or walnuts, if using.
Serve immediately with lemon wedges for squeezing over the top.