In dimensions $$d \in \{3,4,5,6,7\}$$
d
∈
{
3
,
4
,
5
,
6
,
7
}
, we prove that the constant functions on the unit sphere $$\mathbb {S}^{d-1}\subset \mathbb {R}^d$$
S
d
-
1
⊂
R
d
maximize the weighted adjoint Fourier restriction inequality $$\begin{aligned} \left| \int _{\mathbb {R}^d} |\widehat{f\sigma }(x)|^4\,\big (1 + g(x)\big )\,\textrm{d}x\right| ^{1/4} \leqslant \textbf{C} \, \Vert f\Vert _{L^2(\mathbb {S}^{d-1})}, \end{aligned}$$
∫
R
d
|
f
σ
^
(
x
)
|
4
(
1
+
g
(
x
)
)
d
x
1
/
4
⩽
C
‖
f
‖
L
2
(
S
d
-
1
)
,
where $$\sigma $$
σ
is the surface measure on $$\mathbb {S}^{d-1}$$
S
d
-
1
, for a suitable class of bounded perturbations $$g:\mathbb {R}^d \rightarrow \mathbb {C}$$
g
:
R
d
→
C
. In such cases we also fully classify the complex-valued maximizers of the inequality. In the unperturbed setting ($$g = \textbf{0}$$
g
=
0
), this was established by Foschi ($$d=3$$
d
=
3
) and by the first and third authors ($$d \in \{4,5,6,7\}$$
d
∈
{
4
,
5
,
6
,
7
}
) in 2015. Our methods also yield a new sharp adjoint restriction inequality on $$\mathbb S^7\subset \mathbb {R}^8$$
S
7
⊂
R
8
.