Preheat oven to 375F and add 1/4" of water to a large casserole baking dish.
Cut acorn squashes in 1/2 from stem to end, then scoop out the seeds. Pierce a few holes in the rind with a fork.
Next, place the squash halves cutside-up in the baking dish, spray with a light coating of cooking oil and generously salt and pepper them. Bake for 30-35 minutes or until they are fork-tender.
While the squash is cooking, warm a saute pan over medium heat and spray with cooking oil. Once the pan is hot, add onions and saute for 3-5 minutes or until they become mostly translucent.
Add water, farro grains and a pinch of salt to the pan, lower heat to medium-low and cover for 20-25 minutes, or until the grains are cooked and tender, and all liquid is soaked up.
Uncover, add greens, pistachios, craisins, and ground sage; fold together until the greens have wilted some, then season with salt & pepper, to taste.
Once the squash comes out of the oven, divide farro-filling between the four halves; then place in the oven for an additional 5 minutes.
In a small mixing bowl, whisk together all tahini dressing ingredients and set aside. When finished baking, cool stuffed-squash for 5 minutes before serving with tahini dressing on the side. Lastly, enjoy!