Cape Cod Lobster Rolls only opened at the tail end of May, but the small takeout restaurant in Onset has already seen a lot of business.

Larry Senna, the restaurant’s co-owner, said he got the idea three years ago, while watching “Shark Tank,” a show about entrepreneurs who pitch their business ventures to potential investors.

“I saw that, and I thought, ‘I should get some money to do that,” Senna said.

Senna said he mentioned the idea to co-owner Melissa Clements, and the two decided to open the restaurant together at 211 Onset Ave. Senna, who is also the program coordinator of the Wareham Boys and Girls club, owns a business a couple doors down, called LS Computers.

Senna said he wanted to create a small restaurant that specialized only in lobster, because every other restaurant “does a little bit of everything, but mine’s strictly lobster.”

“Everybody says it’s the perfect menu, because ... you don’t have much to choose from,” Senna said. “We know what we are. We are lobster. We don’t try to be an expert at everything.”

Of the 10 items on the small menu, seven are lobster-based. The other three items are clam chowder, a stuffed quahog, and a hot dog. The menu also includes a lobster roll -- but, though the restaurant has its own mixture of seasoning and mayonnaise, customers can adjust the roll to their liking.

“Everybody is shocked at that, because they say in other restaurants, the lobster rolls are just the way they come,” Senna said. “I try to make it just the way you like.”

Senna said that, since the restaurant’s opening, business has been booming. He said the small space, which is only open for a total of six hours every day, sees about 20 to 25 customers. On the weekends, when it is open for seven hours, it sees about 60 customers. He expects more business when the tourist season begins in a couple weeks, and is training two new staffers in anticipation of more customers.

As far as increased demand for product goes, Senna said he is all set on the supply front.

“I have two suppliers that are ready to give me as much as I want, when I want it” Senna said. “They are open seven days a week, so I can get something whenever I need it.”

Cape Cod Lobster Rolls is currently open Monday through Friday, from 11 a.m. to 2 p.m. for lunch, and 5:30 p.m. to 8 p.m. for dinner. Weekend hours are 11 a.m. to 8 p.m.