It’s an enduring murder mystery with all the red sauce fixings.

Three years after a killing that shocked Brooklyn, the trial of the suspect in the shooting of Louis Barbati, co-owner of the legendary Gravesend pizzeria L&B Spumoni Gardens, is set to begin in Brooklyn Supreme Court this week.

The feds initially investigated the murder of Barbati outside his Dyker Heights home in June 2016 as a mob hit that may have been part of a battle between two Italian crime families over a stolen pizza sauce recipe.

But the FBI eventually turned the case over to the NYPD, which settled on 43-year-old Andres Fernandez as the prime suspect and labeled the case as a botched robbery.

The cops say Fernandez shot Barbati, who was carrying $15,000 in a bag and a loaf of bread, five times in a robbery turned lethal.

But a lawyer for Fernandez on Monday said the story didn’t add up — noting that Fernandez didn’t know Barbati and that whoever killed him didn’t make off with his bag of cash.

“It’s been three years. The federal government and the New York City Police Department still can’t say why this happened,” attorney Javier Solano told The Post.

“And more importantly, they can’t say why my client would do something like this to Mr. Barbati.”

Surveillance footage allegedly showed the Long Island man and his white Acura at the scene on June 30 — while his cell phone was also traced to Dyker Heights and Spumoni Gardens in Gravesend earlier that day.

When jury selection began on Friday, the Brooklyn district attorney’s office agreed to drop the attempted robbery charge and murder charge associated with the alleged robbery.

The charges against Fernandez now are second-degree murder and criminal possession of a weapon.

In 2009, a former L&B employee stole the recipe for the iconic pizzeria’s sauce and started a competing pie place over in Staten Island — which drew the ire of a reputed Colombo crime family associate who was married to one of L&B’s co-owners.

The dispute was settled at a sit-down at a Panera Bread, where the alleged sauce bandit agreed to fork over $4,000.

L&B was founded by Barbati’s grandfather, Ludovico, in 1939.

The younger Barbati was shot and killed near the side door of his house on 12th Avenue in Dyker Heights at about 7 p.m. on June 30, 2016.

Five months later, Fernandez was picked up by FBI agents who had also worked on cases involving the Columbo and Bonanno crime families, but the feds turned the case over to the Brooklyn district attorney’s office when they couldn’t find a mob connection.