Line a baking tray with parchment paper. Preheat oven to 350ºF.

To make the cauliflower steaks, trim any leaves around the base. Place the cauliflower stem-side down on the cutting board and use a large knife to cut slices, about 1 1/2-inches thick. Reserve any small florets that come apart; you can toss them into the sauce.

Drizzle a tablespoon of oil on the parchment paper and spread it with your hands. Arrange the cauliflower steaks on the tray and drizzle with another tablespoon of oil. Rub each steak to coat with oil. Sprinkle with salt and pepper. Bake for about 30 minutes, until the core can be easily pierced with a knife. Increase temperature to 425ºF and roast for another 15 to 20 minutes, until the cauliflower is deep golden brown and crisp around the edges. Remove from the oven when done.

While the cauliflower is cooking, make the sauce. In a large pot, heat the remaining tablespoon of oil on medium heat. Add the onion and 1/2 teaspoon of salt. Cook for 5 to 8 minutes, while stirring occasionally. Stir in the garlic, oregano, paprika, and chili flakes, and cook for another minute or two until fragrant. Stir in the lentils and water. Bring to a boil then reduce heat to a simmer. Cover and simmer for about 15 minutes, until the lentils are tender, but not mushy; they should still have some texture and a little bite to them. Add the crushed tomatoes, olives, and capers. Simmer for another 10 minutes, until the lentils are soft and the flavors have had a chance to mingle. Stir in the lemon juice and remove from heat. Taste and adjust seasonings.

Arrange cauliflower steaks on cooked pasta on individual plates or on a serving platter. Generously spoon sauce over everything. Garnish with parsley.