Imagine a place where the aroma of freshly baked goods wafts through the air, drawing you in like a cartoon character floating on the scent trail. That’s Baker’s Bakery & Cafe in Custer, South Dakota.

That’s Ruby Donut in Ayer, Massachusetts. Nestled in a modest strip mall, Ruby Donut doesn’t scream for attention. But boy, does it deserve it. This unassuming shop, with its simple storefront and ...