If serving the stew with pasta, cook the pasta in salted water until just al dente, according to package directions.
Meanwhile, preheat the oven to 400 degrees F. Place the sliced tomatoes into a roasting pan (used an 8x8 glass roasting dish) and drizzle with 1 tbsp of the olive oil, 1/2 tsp kosher salt, and black pepper to taste. Toss with a spoon.
Place dish into oven and cook for approx 25 minutes or until the tomatoes have released their juices and the skins have started to wilt. Remove from oven .
Meanwhile, in large pan or pot, add the sliced or chopped onions with the remaining 1 tbsp olive oil and 1 tsp kosher salt and cook over medium heat, stirring every few minutes. Cook until the onions have lightly browned along the edges and are tender.
Add the white beans, chopped sun-dried tomatoes, tomato paste, garlic powder, and dried oregano to the pan with onions, and stir gently to incorporate.
Then add the roasted tomatoes from the oven into the pan (along with their juices from the roasting pan) as well as the fresh parsley, baby spinach, olives, and lemon juice and gently stir.
If desired, add the vegetable broth to thin the consistency to your liking. The baby spinach will start wilting as you stir. Taste for seasoning, adding more pepper if desired.
Top with fresh thyme leaves and serve with pasta, if using.