Melt a generous tablespoon of butter in a large saucepan over a low heat. Finely dice the onion and thinly slice the garlic. Add to the saucepan. Sweat gently for a few minutes in the melted butter until tender and fragrant.
Step 2
Add the thawed chopped spinach to the saucepan. Add the lemon zest and stir well to combine. Season the spinach mixture with salt and pepper, adding more or less as desired. Cook over a medium heat for a few minutes until the spinach is hot through.
Step 3
Add the sour cream and grated parmesan to the saucepan. Stir well to combine. Cook the spinach through for a few minutes more over a medium heat until rich and creamy and there is little liquid left in the pan. Serve hot.