I did this in the slow cooker and substituted some of the spices, used kale instead of spinach, increased the carrots and onions and omitted the cauliflower (didn't have any) and got a delicious stew.
For the spices, I used more freshly ground coriander than was advised, I increased it to two teaspoons. I used the cinnamon and ground pepper as advised, but no turmeric or cumin. Instead I used about a tablespoon of fresh, minced ginger and a 1/4 teaspoon allspice, and a dash of cayenne pepper. These gave it more of an Ethiopian flavor.
I reduced the liquid by two cups and the stew is not very liquid-y. I could have kept those 2 cups, but the stew is very, very tasty anyway.
I only used a 14 oz can of tomatoes. I used tomato paste but accidentally had bought tomato paste with pesto in it (garlic, basil, oregano). I used it anyway.
I used 4 cups chopped fresh kale instead of spinach, and no cauliflower.
I cooked the onions and carrots and garlic and spices as directed before putting them in the slow cooker pot with everything else, including the kale and lemon juice. Then I left it in the fridge overnight, then put it in the slowcooker on low for 8 hours. But it probably only needed about 4-5 hours on low.
It's delicious. I would make it again, maybe trying the actual recipe!