Crush the garlic and finely chop the onion. Melt the butter in a skillet over a low/medium heat and add the garlic and onion, sweating gently until tender.
Dice the tomato and add to the skillet along with the cauliflower rice, lemon juice and zest. Stir well to combine.
Add the stock and bring to a simmer. Simmer for 5 or so minutes until all the liquid has evaporated and the rice is hot through.
Add the anchovies and chili flakes. Stir to combine, cooking until the anchovies have melted.
Add the spinach and basil and stir. Cook until the spinach has just wilted.
Scatter with grated parmesan to serve.