In a large pot over medium heat, add a drizzle of oil. Add the sliced smoked sausage and cook until browned on both sides, about 3-4 minutes.
Stir in the diced onion and minced garlic, cooking until softened, about 2-3 minutes.
Pour in the vegetable broth and add the cubed baby potatoes. Bring to a boil, then reduce heat and let simmer until potatoes are fork-tender, about 10-12 minutes.
Stir in the diced tomatoes and Cajun seasoning. Let simmer for 5 minutes to blend the flavors.
Drain the baby corn and add it to the pot. Stir in the shrimp and cook for 3-4 minutes, or until pink and opaque.
Remove from heat and stir in the freshly squeezed lemon juice.
Brown the sausage first: Let it get a little color before adding the onion and garlic. Those browned bits add a lot of flavor to the broth.
Cut potatoes evenly: Halve baby potatoes so they cook at the same speed. If some are larger, quarter them so everything finishes together.
Do not overcook the shrimp: Add shrimp at the end and cook just until pink, then turn off the heat. The hot broth will finish cooking it without turning it rubbery.
Season in layers: Cajun blends vary a lot in salt and heat, so start with a little less, simmer, then taste before adding more.
Add lemon last: Stir in lemon juice off the heat for the freshest flavor. If you add it too early, it can taste muted.
Make it ahead the right way: If prepping in advance, cook everything except the shrimp, then reheat and add shrimp right before serving for the best texture.