Preheat the oven to 450°F. Trim the leaves from the cauliflower and remove 1 inch off the bottom of the stem. Carefully cut the cauliflower into 4 “steaks,” about 1 inch thick. Transfer them to a baking sheet and coat with 1 tbsp vegetable oil, total. Season both sides with the dried oregano and a pinch of salt and pepper. Roast until crisp in places and well browned, about 18 to 24 minutes.
Peel and thinly slice the shallot. Thinly slice the celery. Pick the parsley leaves from the stems. Add the shallot, celery, and parsley leaves to a medium bowl with the juice from half the lemon, and 1 tbsp olive oil. Season with salt and toss to coat.
Peel the garlic. Drain the roasted red peppers and add them to a blender. Add the garlic, just ¼ cup of the pepitas, remaining lemon juice, 2 tbsp olive oil, 1 tbsp water, and a pinch of salt and pepper. Blend the pepita romesco sauce on high, scraping down the sides as necessary, until smooth.
Place a large nonstick skillet over medium heat and add the remaining pepitas. Cook, tossing occasionally, until toasted and fragrant, about 3 to 5 minutes. Transfer the toasted pepitas to a small bowl.
Drain, rinse, and pat the butter beans dry with paper towels. Return the large nonstick skillet to medium-high heat with 1 tbsp olive oil. Once it’s hot, add the butter beans and a pinch of salt and pepper cook, shaking the pan occasionally, until crisp in places, about 2 to 4 minutes.
Spread the pepita romesco sauce on large plates and top with crispy butter beans and the cauliflower steaks. Top with the celery salad and sprinkle with toasted pepitas. Enjoy!