  We present new VLTI/GRAVITY near-infrared interferometric measurements of the
angular size of the innermost hot dust continuum for 14 type 1 AGNs. The
angular sizes are resolved on scales of ~0.7 mas and the inferred ring radii
range from 0.028 to 1.33 pc, comparable to those reported previously and a
factor 10-20 smaller than the mid-infrared sizes in the literature. Combining
our new data with previously published values, we compile a sample of 25 AGN
with bolometric luminosity ranging from $10^{42}$ to $10^{47} \rm erg~s^{-1}$,
with which we study the radius-luminosity (R-L) relation for the hot dust
structure. Our interferometric measurements of radius are offset by a factor 2
from the equivalent relation derived through reverberation mapping. Using a
simple model to explore the dust structure's geometry, we conclude that this
offset can be explained if the 2 um emitting surface has a concave shape. Our
data show that the slope of the relation is in line with the canonical $R
\propto L^{0.5}$ when using an appropriately non-linear correction for
bolometric luminosity. In contrast, using optical luminosity or applying a
constant bolometric correction to it results in a significant deviation in the
slope, suggesting a potential luminosity dependence on the spectral energy
distribution. Over four orders of magnitude in luminosity, the intrinsic
scatter around the R-L relation is 0.2 dex, suggesting a tight correlation
between innermost hot dust structure size and the AGN luminosity.
