Pre-cooked polenta, made from cornmeal, makes a great base for vegetarian dinners and holds up well to flavorful sauces like this mushroom ragu. (Note: For more variations, look for polenta in a variety of flavors like sun-dried tomato and garlic-herb.)
Heat a skillet or saute pan over medium-high heat and add oil (just the portion for the polenta). When oil begins to shimmer, add polenta. Sear until golden brown and heated through, 4 to 5 minutes on each side. Transfer polenta to a plate and cover with foil so it stays warm.
Return skillet to heat. Add oil (the portion for the sauce) and mushrooms and saute until mushrooms are tender and golden brown, ~5 minutes. Add onions, peppers, garlic (the portion for the ragu) and saute until tender, ~4 minutes. Add tomato paste, diced tomatoes (including liquid), basil and vinegar and stir to combine. Bring to a boil and continue cooking until sauce thickens slightly, ~2 minutes. Season with some salt and pepper (and a pinch of sugar, if needed).
Place trimmed green beans and garlic in a microwave-safe dish. Cover with a wet paper towel and microwave for 1 1/2 to 2 minutes, until tender but still crunchy. Season with some salt and pepper and squeeze lemon juice over top.
Enjoy polenta with ragu and grated parmesan over top and green beans on the side.