Preheat oven to 350F.  Clean and remove the leaves from the cauliflower and cut the bottom so it will sit flat.  Slice the cauliflower vertically into 3/4 inch slices.  Brush both sides of the slices with olive oil, salt and pepper.  In a cast iron grill pan cook for 5-8 minutes on each side until it starts to brown slightly.  (You could also use a George Foreman Grill or something similar).  Put the cast iron pan into the oven for 30 minutes, covered.  (Or transfer from grill onto a baking sheet and into the oven).  

While that is cooking, prepare the sauce. Combine tahini, garlic, lemon juice, nutritional yeast, olive oil, water, and salt in a food processor or high speed blender until smooth.

Next, in a medium sized pan, heat olive oil on medium. Add diced onion and saute 5 minutes. Add the chickpeas and sun-dried tomatoes and saute for 10 minutes. 

Remove the cauliflower steaks from the oven. Top each slice with the chickpea and sun-dried tomato mixture. Drizzle with the tahini sauce. Enjoy!