CSS pseudo element before coming on top of the container instead behind of container.

<Box className={styles.celebrityNights}>
  <Typography sx={{fontSize: '3rem'}}>Dj Shameless Mani</Typography>
  <Typography sx={{fontSize: '1.6rem'}}>10th March</Typography>
</Box>

.celebrityNights {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  text-align: center;
  cursor: default;
  padding: 1rem;
  position: relative;
  background: #17181F;
  overflow: hidden;
}

.celebrityNights::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(#4150d0, #c850c0);
}