Endrick's well-taken strike earned Real Madrid a 1-0 win at Real Sociedad in a tight Copa del Rey semifinal first leg clash on Wednesday.
However there was controversy when just before halftime the match was briefly paused because of chants of "Asencio die" being aimed at Real Madrid defender Raul Asencio, according to Spanish media.
A video subsequently emerged on social media of a Real Sociedad fan appearing to make monkey gestures at Vinicius Junior while the game was stopped.
Spanish and European champions Madrid took control of the tie ahead of the second leg on April 1 at their Santiago Bernabeu stadium.
Endrick pounced after 19 minutes, finishing with the outside of his boot after racing on to Jude Bellingham's diagonal ball, and it was enough to claim his side the win.
Madrid coach Carlo Ancelotti was without French superstar Kylian Mbappe after a dental problem as well as Fede Valverde and Thibaut Courtois.
The Real Madrid boss chose to rotate his side ahead of the visit to face Real Betis in LaLiga on Saturday and next week's Champions League last 16 clash against Atletico Madrid.
Despite his many changes, including starts for Arda Guler, Fran Garcia and Eduardo Camavinga, Madrid put on a solid showing at the Reale Arena in San Sebastian.
Endrick sent Los Blancos ahead when Bellingham sent the 18-year-old attacker in on goal.
After taking one touch to control, with his second Endrick stroked home stylishly at the near post.
It was his sixth goal of the campaign, four of those coming in the Copa del Rey, where Ancelotti has given him the most chance to shine.
Bellingham, who missed Madrid's win against Girona in LaLiga last weekend through suspension, looked fresh and helped his side stay largely on top.
Vinicius came close with a low shot which Alex Remiro tipped to safety.
Madrid goalkeeper Andriy Lunin made a fine double save early in the second half to keep Mikel Oyarzabal and Takefusa Kubo at bay.
Madrid came close to a second at the other end when Endrick crashed a shot against the bar from the edge of the box.
Remiro produced a fine save to push away Bellingham's deflected strike and then another to thwart the same player from long range in the final stages, keeping Real Sociedad's hopes of a second leg comeback alive.
In the other semifinal first leg on Tuesday Atletico Madrid fought back to draw 4-4 with record 31-time cup winners Barcelona.