1) Preheat oven to 425ºF.
2) Line a large baking sheet with parchment paper.
3) Remove all leaves from the head of cauliflower. Cut the stem so you can create a stable base to cut the cauliflower. Stem side down, cut the cauliflower into 1” thick slices, you will get 2-3 cauliflower steaks the rest of the cauliflower will come out as florets and that’s normal. It will all depend on how compact the cauliflower is.
4) Place cauliflower steaks and florets on the baking sheet. Brush each side of the cauliflower steaks with olive oil and drizzle the rest on the florets. Season with salt and oregano.
5) Roast for 45 minutes or until the cauliflower is tender, but still has a bite.
6) While the cauliflower is cooking, prepare the topping. In a large skillet, heat the olive oil, add garlic and parsley and cook on medium heat for 3-4 minutes, add pistachios and pretzels and cook for an additional 3-4 minutes.
7) Place the cauliflower steaks and florets on a serving platter, sprinkle the crunchy topping and squeeze lemon juice on top. Drizzle with a tahini sauce (optional).