Cut the zucchini in half lengthwise, don't trim off the stem ends. Use a teaspoon to carefully scoop the flesh out of the zucchinis (scoop out a lot of the flesh, leaving about 1/4-inch (5mm) border on all sides). Reserve the scooped-out flesh, chop it roughly with a knife, squeeze out excess water.
Dice the bell paprika and onion, chop the garlic very finely.
Preheat the oven to 350°F / 180°C / Gas Mark 4, no fan.
Heat the oil in a large frying pan over medium-low heat. When hot add the bell pepper and onion. Cook, stirring from time to time, for about 3-4 minutes, or until the onion is soft. Add the garlic and cook for 30 seconds more.
Add reserved zucchini flesh. Cook for about 10 minutes over medium-high heat or until most of the moisture is evaporated (zucchini should reduce its volume a lot or the filling won't fit into the boats).
Add ground meat and Fajita seasoning, cook for a couple of minutes over high heat or until the meat is no longer pink.
Add the crushed tomatoes, corn, and beans. Cook for a couple of minutes. Season with salt and pepper to taste.
Fill the zucchini boats with the sauce.
Place the zucchini on a baking sheet and bake for 30 minutes (baking time may vary depending on the thickness of the zucchini boats, zucchini should be tender but still a little bit crunchy).
Take the baking sheet out of the oven and sprinkle the zucchini boats with shredded cheese.
Broil for about a couple of minutes or until the cheese is melted (if you don't have this setting you can turn on grill or fan setting or just bake the zucchinis 10 minutes longer until the cheese is melted).
Drizzle zucchini boats with lime juice.